Method and system to use ac welding waveform and enhanced consumable to improve welding of galvanized workpiece

ABSTRACT

Embodiments of the present invention comprise a system and method to weld or join coated materials using an arc welding system alone, or in combination with a hot wire system, where the arc welding system uses a welding current having an AC current portion to build a droplet for transfer to the workpiece. In further embodiments, the workpiece is coated with a material, such as zinc, and the arc welding system uses an AC welding waveform which is capable of welding coated workpieces with little or no porosity or spatter and can achieve enhanced performance. Additional embodiments use an enhanced electrode to provide optimum porosity performance. Such embodiments allow for the welding of coated material with little or no porosity and spatter, and at a high welding rate.

PRIORITY

The present application claims priority to Provisional Application No.61/975,227 filed on Apr. 4, 2014, which is incorporated herein byreference in its entirety.

TECHNICAL FIELD

Certain embodiments relate to welding and joining applications. Moreparticularly, certain embodiments relate to a system and method to usean enhanced AC welding waveform, with or without an enhanced consumable,to weld or join galvanized workpieces at a high rate with little or noporosity.

BACKGROUND

Many different welding methods and systems are used to join workpieceswhich have a corrosion resistance coating, such as galvanizedworkpieces. However, because of the presence of the corrosion resistancecoating, these methods and systems are limited in their use.Specifically, these systems and methods typically are slow, to ensurethat the coating does not overly contaminate the weld. However, becausethese processes are slow they tend to increase the heat input into theweld joint. This is undesirable, particularly in applications where theworkpieces are relatively thin.

Further limitations and disadvantages of conventional, traditional, andproposed approaches will become apparent to one of skill in the art,through comparison of such approaches with embodiments of the presentinvention as set forth in the remainder of the present application withreference to the drawings.

SUMMARY

Embodiments of the present invention comprise a system and method toweld or join coated materials using an arc welding system alone, or incombination with a hot wire system, where the arc welding system uses awelding current having an AC current portion to build a droplet fortransfer to the workpiece. In further embodiments, the workpiece iscoated with a material, such as zinc, and the arc welding system uses anAC welding waveform which is capable of welding coated workpieces withlittle or no porosity or spatter and can achieve enhanced performance.Such embodiments allow for the welding of coated material with little orno porosity and spatter, and at a high welding rate.

These and other features of the claimed invention, as well as details ofillustrated embodiments thereof, will be more fully understood from thefollowing description and drawings.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 illustrates a functional schematic block diagram of an exemplaryembodiment of a combination filler wire feeder and energy source systemfor any of brazing, cladding, building up, filling, and hard-facingoverlaying applications;

FIG. 2 illustrates a flow chart of an embodiment of a start-up methodused by the system of FIG. 1;

FIG. 3 illustrates a flow chart of an embodiment of a post start-upmethod used by the system of FIG. 1;

FIG. 4 illustrates a first exemplary embodiment of a pair of voltage andcurrent waveforms associated with the post start-up method of FIG. 3;

FIG. 5 illustrates a second exemplary embodiment of a pair of voltageand current waveforms associated with the post start-up method of FIG.3;

FIGS. 6 and 6A illustrate a further exemplary embodiment of the presentinvention used to perform a welding operation;

FIGS. 7, 7A, and 7B illustrate additional exemplary embodiments ofwelding with the present invention;

FIG. 8 illustrates a further exemplary embodiment of joining two sidesof a joint at the same time;

FIG. 9 illustrates another exemplary embodiment of welding with thepresent invention;

FIG. 10 illustrates another exemplary embodiment of the presentinvention in welding a joint with multiple lasers and wires;

FIGS. 11A to 11C depict exemplary embodiments of contact tips used withembodiments of the present invention;

FIG. 12 illustrates a hot wire power supply system in accordance with anembodiment of the present invention;

FIGS. 13A-C illustrate voltage and current waveforms created byexemplary embodiments of the present invention;

FIG. 14 illustrates another welding system in accordance an exemplaryembodiment of the present invention;

FIG. 15 illustrates an exemplary embodiment of a weld puddle created byan embodiment of the present invention;

FIGS. 16A to 16F illustrate exemplary embodiments of weld puddles andlaser beam utilization in accordance with embodiments of the presentinvention;

FIG. 17 illustrates a welding system in accordance with anotherexemplary embodiment of the present invention;

FIG. 18 illustrates an exemplary embodiment of a ramp down circuit whichcan be used in embodiments of the present invention;

FIG. 19 illustrates an exemplary embodiment of a fume extraction nozzlein accordance with the present invention;

FIG. 20 illustrates an exemplary embodiment of a further welding systemof the present invention;

FIG. 21 illustrates an exemplary embodiment of a welding operation inaccordance with an embodiment of the present invention;

FIG. 22A-22C illustrate exemplary embodiments of current waveformsutilized by welding systems of the present invention;

FIG. 23 illustrates an exemplary embodiment of another welding operationin accordance with an embodiment of the present invention;

FIG. 24 illustrates an another exemplary embodiment of current waveformsthat can be used with embodiments of the present invention;

FIG. 25 illustrates an exemplary embodiment of another welding operationthat can be used with embodiments of the invention;

FIG. 25A illustrates an exemplary embodiment a current waveforms thatcan be used with the embodiment shown in FIG. 25;

FIG. 26 illustrates an exemplary embodiment of a further weldingoperation using side-by-side arc welding operations;

FIG. 27 illustrates an exemplary embodiment of an additional weldingoperation of the present invention;

FIG. 28 illustrates an additional exemplary embodiment of a weldingoperation of the present invention utilizing magnetic steering;

FIG. 29 illustrates an additional exemplary embodiment of an arcgeneration current waveform that can be used with exemplary embodimentsof the present invention; and

FIG. 30 illustrates a further exemplary embodiment of an arc generationcurrent and voltage waveform that can be used with exemplary embodimentsof the present invention

DETAILED DESCRIPTION

The term “overlaying” is used herein in a broad manner and may refer toany applications including brazing, cladding, building up, filling, andhard-facing. For example, in a “brazing” application, a filler metal isdistributed between closely fitting surfaces of a joint via capillaryaction. Whereas, in a “braze welding” application the filler metal ismade to flow into a gap. As used herein, however, both techniques arebroadly referred to as overlaying applications.

FIG. 1 illustrates a functional schematic block diagram of an exemplaryembodiment of a combination filler wire feeder and energy source system100 for performing any of brazing, cladding, building up, filling,hard-facing overlaying, and joining/welding applications. The system 100includes a laser subsystem capable of focusing a laser beam 110 onto aworkpiece 115 to heat the workpiece 115. The laser subsystem is a highintensity energy source. The laser subsystem can be any type of highenergy laser source, including but not limited to carbon dioxide,Nd:YAG, Yb-disk, YB-fiber, fiber delivered or direct diode lasersystems. Further, even white light or quartz laser type systems can beused if they have sufficient energy. Other embodiments of the system mayinclude at least one of an electron beam, a plasma arc weldingsubsystem, a gas tungsten arc welding subsystem, a gas metal arc weldingsubsystem, a flux cored arc welding subsystem, and a submerged arcwelding subsystem serving as the high intensity energy source. Thefollowing specification will repeatedly refer to the laser system, beamand power supply, however, it should be understood that this referenceis exemplary as any high intensity energy source may be used. Forexample, a high intensity energy source can provide at least 500 W/cm².The laser subsystem includes a laser device 120 and a laser power supply130 operatively connected to each other. The laser power supply 130provides power to operate the laser device 120.

The system 100 also includes a hot filler wire feeder subsystem capableof providing at least one resistive filler wire 140 to make contact withthe workpiece 115 in the vicinity of the laser beam 110. Of course, itis understood that by reference to the workpiece 115 herein, the moltenpuddle is considered part of the workpiece 115, thus reference tocontact with the workpiece 115 includes contact with the puddle. The hotfiller wire feeder subsystem includes a filler wire feeder 150, acontact tube 160, and a hot wire power supply 170. During operation, thefiller wire 140, which leads the laser beam 110, is resistance-heated byelectrical current from the hot wire welding power supply 170 which isoperatively connected between the contact tube 160 and the workpiece115. In accordance with an embodiment of the present invention, the hotwire welding power supply 170 is a pulsed direct current (DC) powersupply, although alternating current (AC) or other types of powersupplies are possible as well. The wire 140 is fed from the filler wirefeeder 150 through the contact tube 160 toward the workpiece 115 andextends beyond the tube 160. The extension portion of the wire 140 isresistance-heated such that the extension portion approaches or reachesthe melting point before contacting a weld puddle on the workpiece. Thelaser beam 110 serves to melt some of the base metal of the workpiece115 to form a weld puddle and also to melt the wire 140 onto theworkpiece 115. The power supply 170 provides a large portion of theenergy needed to resistance-melt the filler wire 140. The feedersubsystem may be capable of simultaneously providing one or more wires,in accordance with certain other embodiments of the present invention.For example, a first wire may be used for hard-facing and/or providingcorrosion resistance to the workpiece, and a second wire may be used toadd structure to the workpiece.

The system 100 further includes a motion control subsystem capable ofmoving the laser beam 110 (energy source) and the resistive filler wire140 in a same direction 125 along the workpiece 115 (at least in arelative sense) such that the laser beam 110 and the resistive fillerwire 140 remain in a fixed relation to each other. According to variousembodiments, the relative motion between the workpiece 115 and thelaser/wire combination may be achieved by actually moving the workpiece115 or by moving the laser device 120 and the hot wire feeder subsystem.In FIG. 1, the motion control subsystem includes a motion controller 180operatively connected to a robot 190. The motion controller 180 controlsthe motion of the robot 190. The robot 190 is operatively connected(e.g., mechanically secured) to the workpiece 115 to move the workpiece115 in the direction 125 such that the laser beam 110 and the wire 140effectively travel along the workpiece 115. In accordance with analternative embodiment of the present invention, the laser device 110and the contact tube 160 may be integrated into a single head. The headmay be moved along the workpiece 115 via a motion control subsystemoperatively connected to the head.

In general, there are several methods that a high intensity energysource/hot wire may be moved relative to a workpiece. If the workpieceis round, for example, the high intensity energy source/hot wire may bestationary and the workpiece may be rotated under the high intensityenergy source/hot wire. Alternatively, a robot arm or linear tractor maymove parallel to the round workpiece and, as the workpiece is rotated,the high intensity energy source/hot wire may move continuously or indexonce per revolution to, for example, overlay the surface of the roundworkpiece. If the workpiece is flat or at least not round, the workpiecemay be moved under the high intensity energy source/hot wire as shown ifFIG. 1. However, a robot arm or linear tractor or even a beam-mountedcarriage may be used to move a high intensity energy source/hot wirehead relative to the workpiece.

The system 100 further includes a sensing and current control subsystem195 which is operatively connected to the workpiece 115 and the contacttube 160 (i.e., effectively connected to the output of the hot wirepower supply 170) and is capable of measuring a potential difference(i.e., a voltage V) between and a current (I) through the workpiece 115and the hot wire 140. The sensing and current control subsystem 195 mayfurther be capable of calculating a resistance value (R=V/I) and/or apower value (P=V*I) from the measured voltage and current. In general,when the hot wire 140 is in contact with the workpiece 115, thepotential difference between the hot wire 140 and the workpiece 115 iszero volts or very nearly zero volts. As a result, the sensing andcurrent control subsystem 195 is capable of sensing when the resistivefiller wire 140 is in contact with the workpiece 115 and is operativelyconnected to the hot wire power supply 170 to be further capable ofcontrolling the flow of current through the resistive filler wire 140 inresponse to the sensing, as is described in more detail later herein. Inaccordance with another embodiment of the present invention, the sensingand current controller 195 may be an integral part of the hot wire powersupply 170.

In accordance with an embodiment of the present invention, the motioncontroller 180 may further be operatively connected to the laser powersupply 130 and/or the sensing and current controller 195. In thismanner, the motion controller 180 and the laser power supply 130 maycommunicate with each other such that the laser power supply 130 knowswhen the workpiece 115 is moving and such that the motion controller 180knows if the laser device 120 is active. Similarly, in this manner, themotion controller 180 and the sensing and current controller 195 maycommunicate with each other such that the sensing and current controller195 knows when the workpiece 115 is moving and such that the motioncontroller 180 knows if the hot filler wire feeder subsystem is active.Such communications may be used to coordinate activities between thevarious subsystems of the system 100.

FIG. 2 illustrates a flow chart of an embodiment of a start-up method200 used by the system 100 of FIG. 1. In step 210, apply a sensingvoltage between at least one resistive filler wire 140 and a workpiece115 via a power source 170. The sensing voltage may be applied by thehot wire power supply 170 under the command of the sensing and currentcontroller 195. Furthermore, the applied sensing voltage does notprovide enough energy to significantly heat the wire 140, in accordancewith an embodiment of the present invention. In step 220, advance adistal end of the at least one resistive filler wire 140 toward theworkpiece 115. The advancing is performed by the wire feeder 150. Instep 230, sense when the distal end of the at least one resistive fillerwire 140 first makes contact with the workpiece 115. For example, thesensing and current controller 195 may command the hot wire power supply170 to provide a very low level of current (e.g., 3 to 5 amps) throughthe hot wire 140. Such sensing may be accomplished by the sensing andcurrent controller 195 measuring a potential difference of about zerovolts (e.g., 0.4V) between the filler wire 140 (e.g., via the contacttube 160) and the workpiece 115. When the distal end of the filler wire140 is shorted to the workpiece 115 (i.e., makes contact with theworkpiece), a significant voltage level (above zero volts) may not existbetween the filler wire 140 and the workpiece 115.

In step 240, turn off the power source 170 to the at least one resistivefiller wire 140 over a defined time interval (e.g., severalmilliseconds) in response to the sensing. The sensing and currentcontroller 195 may command the power source 170 to turn off. In step250, turn on the power source 170 at an end of the defined time intervalto apply a flow of heating current through the at least one resistivefiller wire 140. The sensing and current controller 195 may command thepower source 170 to turn on. In step 260, apply energy from a highintensity energy source 110 to the workpiece 115 to heat the workpiece115 at least while applying the flow of heating current.

As an option, the method 200 may include stopping the advancing of thewire 140 in response to the sensing, restarting the advancing (i.e.,re-advancing) of the wire 140 at the end of the defined time interval,and verifying that the distal end of the filler wire 140 is still incontact with the workpiece 115 before applying the flow of heatingcurrent. The sensing and current controller 195 may command the wirefeeder 150 to stop feeding and command the system 100 to wait (e.g.,several milliseconds). In such an embodiment, the sensing and currentcontroller 195 is operatively connected to the wire feeder 150 in orderto command the wire feeder 150 to start and stop. The sensing andcurrent controller 195 may command the hot wire power supply 170 toapply the heating current to heat the wire 140 and to again feed thewire 140 toward the workpiece 115.

Once the start up method is completed, the system 100 may enter a poststart-up mode of operation where the laser beam 110 and hot wire 140 aremoved in relation to the workpiece 115 to perform one of a brazingapplication, a cladding application, a build-up application, ahard-facing application, or a welding/joining operation. FIG. 3illustrates a flow chart of an embodiment of a post start-up method 300used by the system 100 of FIG. 1. In step 310, move a high intensityenergy source (e.g., laser device 120) and at least one resistive fillerwire 140 along a workpiece 115 such that the distal end of the at leastone resistive filler wire 140 leads or coincides with the high intensityenergy source (e.g., laser device 120) such that energy (e.g., laserbeam 110) from the high intensity energy source (e.g., laser device 120)and/or the heated workpiece 115 (i.e., the workpiece 115 is heated bythe laser beam 110) melts the distal end of the filler wire 140 onto theworkpiece 115 as the at least one resistive filler wire 140 is fedtoward the workpiece 115. The motion controller 180 commands the robot190 to move the workpiece 115 in relation to the laser beam 110 and thehot wire 140. The laser power supply 130 provides the power to operatethe laser device 120 to form the laser beam 110. The hot wire powersupply 170 provides electric current to the hot wire 140 as commanded bythe sensing and current controller 195.

In step 320, sense whenever the distal end of the at least one resistivefiller wire 140 is about to lose contact with the workpiece 115 (i.e.,provide a premonition capability). Such sensing may be accomplished by apremonition circuit within the sensing and current controller 195measuring a rate of change of one of a potential difference between(dv/dt), a current through (di/dt), a resistance between (dr/dt), or apower through (dp/dt) the filler wire 140 and the workpiece 115. Whenthe rate of change exceeds a predefined value, the sensing and currentcontroller 195 formally predicts that loss of contact is about to occur.Such premonition circuits are well known in the art for arc welding.

When the distal end of the wire 140 becomes highly molten due toheating, the distal end may begin to pinch off from the wire 140 ontothe workpiece 115. For example, at that time, the potential differenceor voltage increases because the cross section of the distal end of thewire decreases rapidly as it is pinching off. Therefore, by measuringsuch a rate of change, the system 100 may anticipate when the distal endis about to pinch off and lose contact with the workpiece 115. Also, ifcontact is fully lost, a potential difference (i.e., a voltage level)which is significantly greater than zero volts may be measured by thesensing and current controller 195. This potential difference couldcause an arc to form (which is undesirable) between the new distal endof the wire 140 and the workpiece 115 if the action in step 330 is nottaken. Of course, in other embodiments the wire 140 may not show anyappreciable pinching but will rather flow into the puddle in acontinuous fashion while maintaining a nearly constant cross-sectioninto the puddle.

In step 330, turn off (or at least greatly reduce, for example, by 95%)the flow of heating current through the at least one resistive fillerwire 140 in response to sensing that the distal end of the at least oneresistive filler wire 140 is about to lose contact with the workpiece115. When the sensing and current controller 195 determines that contactis about to be lost, the controller 195 commands the hot wire powersupply 170 to shut off (or at least greatly reduce) the current suppliedto the hot wire 140. In this way, the formation of an unwanted arc isavoided, preventing any undesired effects such as splatter orburnthrough from occurring.

In step 340, sense whenever the distal end of the at least one resistivefiller wire 140 again makes contact with the workpiece 115 due to thewire 140 continuing to advance toward the workpiece 115. Such sensingmay be accomplished by the sensing and current controller 195 measuringa potential difference of about zero volts between the filler wire 140(e.g., via the contact tube 160) and the workpiece 115. When the distalend of the filler wire 140 is shorted to the workpiece 115 (i.e., makescontact with the workpiece), a significant voltage level above zerovolts may not exist between the filler wire 140 and the workpiece 115.The phrase “again makes contact” is used herein to refer to thesituation where the wire 140 advances toward the workpiece 115 and themeasured voltage between the wire 140 (e.g., via the contact tube 160)and the workpiece 115 is about zero volts, whether or not the distal endof the wire 140 actually fully pinches off from the workpiece 115 ornot. In step 350, re-apply the flow of heating current through the atleast one resistive filler wire in response to sensing that the distalend of the at least one resistive filler wire again makes contact withthe workpiece. The sensing and current controller 195 may command thehot wire power supply 170 to re-apply the heating current to continue toheat the wire 140. This process may continue for the duration of theoverlaying application.

For example, FIG. 4 illustrates a first exemplary embodiment of a pairof voltage and current waveforms 410 and 420, respectively, associatedwith the post start-up method 300 of FIG. 3. The voltage waveform 410 ismeasured by the sensing and current controller 195 between the contacttube 160 and the workpiece 115. The current waveform 420 is measured bythe sensing and current controller 195 through the wire 140 andworkpiece 115.

Whenever the distal end of the resistive filler wire 140 is about tolose contact with the workpiece 115, the rate of change of the voltagewaveform 410 (i.e., dv/dt) will exceed a predetermined threshold value,indicating that pinch off is about to occur (see the slope at point 411of the waveform 410). As alternatives, a rate of change of currentthrough (di/dt), a rate of change of resistance between (dr/dt), or arate of change of power through (dp/dt) the filler wire 140 and theworkpiece 115 may instead be used to indicate that pinch off is about tooccur. Such rate of change premonition techniques are well known in theart. At that point in time, the sensing and current controller 195 willcommand the hot wire power supply 170 to turn off (or at least greatlyreduce) the flow of current through the wire 140.

When the sensing and current controller 195 senses that the distal endof the filler wire 140 again makes good contact with the workpiece 115after some time interval 430 (e.g., the voltage level drops back toabout zero volts at point 412), the sensing and current controller 195commands the hot wire power supply 170 to ramp up the flow of current(see ramp 425) through the resistive filler wire 140 toward apredetermined output current level 450. In accordance with an embodimentof the present invention, the ramping up starts from a set point value440. This process repeats as the energy source 120 and wire 140 moverelative to the workpiece 115 and as the wire 140 advances towards theworkpiece 115 due to the wire feeder 150. In this manner, contactbetween the distal end of the wire 140 and the workpiece 115 is largelymaintained and an arc is prevented from forming between the distal endof the wire 140 and the workpiece 115. Ramping of the heating currenthelps to prevent inadvertently interpreting a rate of change of voltageas a pinch off condition or an arcing condition when no such conditionexists. Any large change of current may cause a faulty voltage readingto be taken due to the inductance in the heating circuit. When thecurrent is ramped up gradually, the effect of inductance is reduced.

FIG. 5 illustrates a second exemplary embodiment of a pair of voltageand current waveforms 510 and 520, respectively, associated with thepost start-up method of FIG. 3. The voltage waveform 510 is measured bythe sensing and current controller 195 between the contact tube 160 andthe workpiece 115. The current waveform 520 is measured by the sensingand current controller 195 through the wire 140 and workpiece 115.

Whenever the distal end of the resistive filler wire 140 is about tolose contact with the workpiece 115, the rate of change of the voltagewaveform 510 (i.e., dv/dt) will exceed a predetermined threshold value,indicating that pinch off is about to occur (see the slope at point 511of the waveform 510). As alternatives, a rate of change of currentthrough (di/dt), a rate of change of resistance between (dr/dt), or arate of change of power through (dp/dt) the filler wire 140 and theworkpiece 115 may instead be used to indicate that pinch off is about tooccur. Such rate of change premonition techniques are well known in theart. At that point in time, the sensing and current controller 195 willcommand the hot wire power supply 170 to turn off (or at least greatlyreduce) the flow of current through the wire 140.

When the sensing and current controller 195 senses that the distal endof the filler wire 140 again makes good contact with the workpiece 115after some time interval 530 (e.g., the voltage level drops back toabout zero volts at point 512), the sensing and current controller 195commands the hot wire power supply 170 to apply the flow of heatingcurrent (see heating current level 525) through the resistive fillerwire 140. This process repeats as the energy source 120 and wire 140move relative to the workpiece 115 and as the wire 140 advances towardsthe workpiece 115 due to the wire feeder 150. In this manner, contactbetween the distal end of the wire 140 and the workpiece 115 is largelymaintained and an arc is prevented from forming between the distal endof the wire 140 and the workpiece 115. Since the heating current is notbeing gradually ramped in this case, certain voltage readings may beignored as being inadvertent or faulty due to the inductance in theheating circuit.

In summary, a method and system to start and use a combination wire feedand energy source system for any of brazing, cladding, building up,filling, and hard-facing overlaying applications are disclosed. Highintensity energy is applied onto a workpiece to heat the workpiece. Oneor more resistive filler wires are fed toward the workpiece at or justin front of the applied high intensity energy. Sensing of when a distalend of the one or more resistive filler wires makes contact with theworkpiece at or near the applied high intensity energy is accomplished.Electric heating current to the one or more resistive filler wires iscontrolled based on whether or not the distal end of the one or moreresistive filler wires is in contact with the workpiece. The appliedhigh intensity energy and the one or more resistive filler wires aremoved in a same direction along the workpiece in a fixed relation toeach other.

In further exemplary embodiments, systems and methods of the presentinvention are employed for welding or joining operations. Theembodiments discussed above have focused on the use of filler metals inoverlaying operations. However, aspects of the present invention can beused in welding and joining applications in which workpieces are joinedusing welding operations and the use of a filler metal. Althoughdirected to overlaying a filler metal, the above described embodiments,systems and methods are similar to that employed in welding operations,described more fully below. Therefore, in the following discussions itis understood that the discussions above generally apply, unlessotherwise stated. Further, the following discussion may includereference to FIGS. 1 through 5.

It is known that welding/joining operations typically join multipleworkpieces together in a welding operation where a filler metal iscombined with at least some of the workpiece metal to form a joint.Because of the desire to increase production throughput in weldingoperations, there is a constant need for faster welding operations,which do not result in welds which have a substandard quality.Furthermore, there is a need to provide systems which can weld quicklyunder adverse environmental conditions, such as in remote work sites. Asdescribed below, exemplary embodiments of the present invention providesignificant advantages over existing welding technologies. Suchadvantages include, but are not limited to, reduced total heat inputresulting in low distortion of the workpiece, very high welding travelspeeds, very low spatter rates, welding with the absence of shielding,welding plated or coated materials at high speeds with little or nospatter and welding complex materials at high speeds.

In exemplary embodiments of the present invention, very high weldingspeeds, as compared to arc welding, can be obtained using coatedworkpieces, which typically require significant prep work and are muchslower welding processes using arc welding methods. As an example, thefollowing discussion will focus on welding galvanized workpieces.Galvanization of metal is used in increase the corrosion resistance ofthe metal and is desirable in many industrial applications. However,conventional welding of galvanized workpieces can be problematic.Specifically, during welding the zinc in the galvanization vaporizes andthis zinc vapor can become trapped in the weld puddle as the puddlesolidifies, causing porosity. This porosity adversely affects thestrength of the weld joint. Because of this, existing welding techniquesrequire a first step of removing the galvanization or welding throughthe galvanization at lower processing speeds and with some level ofdefects—which is inefficient and causes delay, or requires the weldingprocess to proceed slowly. By slowing the process the weld puddleremains molten for a longer period of time allowing the vaporized zincto escape. However, because of the slow speed production rates are slowand the overall heat input into the weld can be high. Other coatingswhich can cause similar issues include, but are not limited to: paint,stamping lubricants, glass linings, aluminized coatings, surface heattreatment, nitriding or carbonizing treatments, cladding treatments, orother vaporizing coatings or materials. Exemplary embodiments of thepresent invention eliminate these issues, as explained below.

Turning to FIGS. 6 and 6A (cross-section and side view, respectively) arepresentative welding lap joint is shown. In this figure two coated(e.g., galvanized) workpieces W1/W2 are to be joined with a lap weld.The lap joint surfaces 601 and 603 are initially covered with thecoating as well as the surface 605 of workpiece W1. In a typical weldingoperation (for example GMAW) portions of the covered surface 605 aremade molten. This is because of the typical depth of penetration of astandard welding operation. Because the surface 605 is melted thecoating on the surface 605 is vaporized, but because of the distance ofthe surface 605 from the surface of the weld pool is large, the gasescan be trapped as the weld pool solidifies. With embodiments of thepresent invention this does not occur.

As shown in FIGS. 6 and 6A a laser beam 110 is directed from the laserdevice 120 to the weld joint, specifically the surfaces 601 and 603. Thelaser beam 110 is of an energy density to melt portions of the weldsurfaces creating molten puddles 601A and 603A, which creates a generalweld puddle. Further, a filler wire 140—which is resistance heated asdescribed previously—is directed to the weld puddle to provide theneeded filler material for the weld bead. Unlike most welding processesthe filler wire 140 makes contact and is plunged into the weld puddleduring the welding process. This is because this process does not use awelding arc to transfer the filler wire 140 but rather simply melts thefiller wire into the weld puddle.

Because the filler wire 140 is preheated to at or near its melting pointits presence in the weld puddle will not appreciably cool or solidifythe puddle and is quickly consumed into the weld puddle. The generaloperation and control of the filler wire 140 is as described previouslywith respect to the overlaying embodiments.

Because the laser beam 110 can be precisely focused and directed to thesurfaces 601/603, the depth of penetration for the pools 601A/603A canbe precisely controlled. By controlling this depth carefully,embodiments of the present invention prevent any unnecessary penetrationor melting of the surface 605. Because of the surface 605 is not overlymelted any coating on the surface 605 is not vaporized and does notbecome trapped in the weld puddle. Further, any coating on the surfaceof the weld joint 601 and 603 are easily vaporized by the laser beam 110and that gas is allowed to escape the weld zone before the weld puddlesolidifies. It is contemplated that a gas extraction system can beutilized to aid in the removal of any vaporized coating materials.

Because the depth of weld puddle penetration can be precisely controlledthe speed of welding coated workpieces can be greatly increased, whilesignificantly minimizing or eliminating porosity. Some arc weldingsystem can achieve good travel speeds for welding, but at the higherspeeds problems can occur such as porosity and spatter. In exemplaryembodiments of the present invention, very high travel speeds can beachieved with little or no porosity or spatter (as discussed herein) andin fact travel speeds of over 50 inches/min can be easily achieved formany different types of welding operations. Embodiments of the presentinvention can achieve welding travel speeds over 80 inches/minute.Further, other embodiments can achieve travel speeds in the range of 100to 150 inches/min with minimal or no porosity or spatter, as discussedherein. Of course, the speeds achieved will be a function of theworkpiece properties (thickness and composition) and the wire properties(e.g., dia.), but these speeds are readily achievable in many differentwelding and joining applications when using embodiments of the presentinvention. Further, these speeds can be achieved with either a 100%carbon dioxide shielding gas, or can be achieved with no shielding atall. Additionally, these travel speeds can be achieved without removingany surface coating prior to the creation of the weld puddle andwelding. Of course, it is contemplated that higher travel speeds can beachieved. Furthermore, because of the reduced heat input into the weldthese high speeds can be achieved in thinner workpieces 115, whichtypically have a slower weld speed because heat input must be kept lowto avoid distortion. Not only can embodiments of the present inventionachieve the above described high travel speeds with little or noporosity or spatter, but they can also achieve very high depositionrates, with low admixture. Specifically, embodiments of the presentinvention can achieve deposition rates of 10 lb/hr or higher with noshielding gas and little or no porosity or spatter. In some embodimentsthe deposition rate is in the range of 10 to 20 lb/hr.

In the exemplary embodiments of the present invention, these extremelyhigh travel speeds are achieved with little or no porosity and little orno spatter. Porosity of a weld can be determined by examining across-section and/or a length of the weld bead to identify porosityratios. The cross-section porosity ratio is the total area of porosityin a given cross-section over the total cross-sectional area of the weldjoint at that point. The length porosity ratio is the total accumulatedlength of pores in a given unit length of weld joint. Embodiments of thepresent invention can achieve the above described travel speeds with across-sectional porosity between 0 and 20%. Thus, a weld bead with nobubbles or cavities will have a 0% porosity. In other exemplaryembodiments, the cross-sectional porosity can be in the range of 0 to10%, and in another exemplary embodiment can be in the range of 2 to 5%.It is understood that in some welding applications some level ofporosity is acceptable. Further, in exemplary embodiments of theinvention the length porosity of the weld is in the range of 0 to 20%,and can be 0 to 10%. In further exemplary embodiments the lengthporosity ratio is in the range of 1 to 5%. Thus, for example, welds canbe produced that have a cross-sectional porosity in the range of 2 to 5%and a length porosity ratio of 1 to 5%.

Furthermore, embodiments of the present invention can weld at the aboveidentified travel speeds with little or no spatter. Spatter occurs whendroplets of the weld puddle are caused to spatter outside of the weldzone. When weld spatter occurs it can compromise the quality of the weldand can cause production delays as it must be typically cleaned off ofthe workpieces after the welding process. Moreover, when a workpiece iscoated, for example is galvanized, the spatter tends to stick to thegalvanization and creates an entry point for corrosion. Thus, there isgreat benefit to welding at high speed with no spatter. Embodiments ofthe present invention are capable of welding at the above high travelspeeds with a spatter factor in the range of 0 to 0.5, where the spatterfactor is the weight of the spatter over a given travel distance X (inmg) over the weight of the consumed filler wire 140 over the samedistance X (in Kg). That is:

Spatter Factor=(spatter weight (mg)/consumed filler wire weight (Kg))

The distance X should be a distance allowing for a representativesampling of the weld joint. That is, if the distance X is too short,e.g., 0.5 inch, it may not be representative of the weld. Thus, a weldjoint with a spatter factor of 0 would have no spatter for the consumedfiller wire over the distance X, and a weld with a spatter of factor of2.5 had 5 mg of spatter for 2 Kg of consumed filler wire. In anexemplary embodiment of the present invention, the spatter factor is inthe range of 0 to 1. In a further exemplary embodiment, the spatterfactor is in the range of 0 to 0.5. In another exemplary embodiment ofthe present invention the spatter factor is in the range of 0 to 0.3. Itshould be noted that embodiments of the present invention can achievethe above described spatter factor ranges with or without the use of anyexternal shielding—which includes either shielding gas or fluxshielding. Furthermore, the above spatter factor ranges can be achievedwhen welding uncoated or coated workpieces, including workpieces whichare galvanized—without having the galvanization removed prior to thewelding operation.

There are a number of methods to measure spatter for a weld joint. Onemethod can include the use of a “spatter boat.” For such a method arepresentative weld sample is placed in a container with a sufficientsize to capture all, or almost all, of the spatter generated by a weldbead. The container or portions of the container—such as the top—canmove with the weld process to ensure that the spatter is captured.Typically the boat is made from copper so the spatter does not stick tothe surfaces. The representative weld is performed above the bottom ofthe container such that any spatter created during the weld will fallinto the container. During the weld the amount of consumed filler wireis monitored. After the weld is completed the spatter boat is to beweighed by a device having sufficient accuracy to determine thedifference, if any, between the pre-weld and post-weld weight of thecontainer. This difference represents the weight of the spatter and isthen divided by the amount, in Kg, of the consumed filler wire.Alternatively, if the spatter does not stick to the boat the spatter canbe removed and weighed by itself.

As described previously, the use of the laser device 120 allows forprecise control of the depth of the weld puddle. Furthermore, the use ofthe laser 120 permits easy adjustment of the size and depth of the weldpuddle. This is because the laser beam 110 can be focused/de-focusedeasily or have its beam intensity changed very easily. Because of theseabilities the heat distribution on the workpieces W1 and W2 can beprecisely controlled. This control allows for the creation of verynarrow weld puddles for precise welding as well as minimizing the sizeof the weld zone on the workpiece. This also provides advantages inminimizing the areas of the workpiece that are not affected by the weldbead. Specifically, the areas of the workpieces adjacent to the weldbead will have minimal affects from the welding operation, which isoften not the case in arc welding operations.

In exemplary embodiments of the present invention, the shape and/orintensity of the beam 110 can be adjusted/changed during the weldingprocess. For example, it may be necessary at certain places on aworkpiece to change the depth of penetration or to change the size ofthe weld bead. In such embodiments the shape, intensity, and/or size ofthe beam 110 can be adjusted during the welding process to provide theneeded change in the welding parameters.

As described above, the filler wire 140 impacts the same weld puddle asthe laser beam 110. In an exemplary embodiment, the filler wire 140impacts the weld puddle at the same location as the laser beam 110.However, in other exemplary embodiments the filler wire 140 can impactthe same weld puddle remotely from the laser beam. In the embodimentshown in FIG. 6A the filler wire 140 trails the beam 110 during thewelding operation. However, that is not necessary as the filler wire 140can be positioned in the leading position. The present invention is notlimited in this regard, as the filler wire 140 can be positioned atother positions relative to the beam 110 so long as the filler wire 140impacts the same weld puddle as the beam 110.

The above described embodiment was described with respect to workpieceswhich have a coating, such as galvanization. However, embodiments of thepresent invention can also be used on workpieces that have no coating.Specifically, the same above described welding process can be utilizedwith non-coated workpieces. Such embodiments achieve the sameperformance attributes as described above regarding coated metals.

Further, exemplary embodiments of the present invention are not limitedto welding steel workpieces, but can also be used for welding aluminum,or more complex metals—as will be described further below.

Another beneficial aspect of the present invention is related toshielding gas. In a typical arc welding operation a shielding gas orshielding flux is used to prevent the oxygen and nitrogen in theatmosphere, or other harmful elements, from interacting with the weldpuddle and metal transfer. Such interference can be detrimental to thequality and appearance of the weld. Therefore, in almost all arc weldingprocesses shielding is provided by the use of externally suppliedshielding gas, shielding gas created by the consumption of an electrodehaving flux on it (e.g., stick electrode, flux cored electrode, etc.) orby an externally supplied granulated flux (e.g., sub-arc welding).Further, in some welding operations, such as welding specialized metalsor welding galvanized work pieces, a special shielding gas mixture mustbe employed. Such mixtures can be extremely expensive. Further, whenwelding in extreme environments it is often difficult to transport largequantities of shielding gas to the work site (such as at pipelines), orwind tends to blow the shielding gas away from the arc. Further, the useof fume extraction systems has grown in recent years. While thesesystems tend to remove fumes they also tend to draw away shielding gasif placed to close to the welding operation.

Benefits of the present invention include being able to use minimalamounts or no shielding gas when welding. Alternatively, embodiments ofthe present invention allow the use of shielding gasses that wouldnormally not be able to be used for a specific welding operation. Thisis discussed further below.

When welding typical workpieces (non-coated) with an arc weldingprocess, shielding—regardless of its form—is required. It has beendiscovered that when welding with embodiments of the present invention,no shielding is required. That is no shielding gas, no granular flux andno self-shielding electrodes need be used. However, unlike in an arcwelding process, the present invention produces a quality weld. That is,the above described weld speeds can be achieved without the use of anyshielding. This could not have been accomplished with prior arc weldingprocesses.

During a typical arc welding process a molten droplet of the filler wireis transferred from the filler wire to the weld puddle through thewelding arc. Without shielding the entire surface of the droplet isexposed to the atmosphere during transfer and as such tends to pick upthe nitrogen and oxygen in the atmosphere and deliver the nitrogen andoxygen to the weld puddle. This is not desirable.

Because the present invention delivers the filler wire to the weldwithout the use of droplets, or similar processes, the filler wire isnot exposed to the atmosphere as much. Therefore, in many weldingapplications the use of shielding is not required. As such, not only canembodiments of the present invention achieve high welding speeds withlittle or no porosity or spatter, they can do so without the use ofshielding gas.

Without having to use shielding, it is possible to locate a fumeextraction nozzle much closer to the weld joint during welding, thusproviding more efficient and effective fume extraction. When a shieldinggas is employed it is necessary to place the fume extraction nozzle at alocation such that it does not interfere with the function of theshielding gas. Because of the advantages of the present invention, nosuch restriction exists and fume extraction can be optimized. Forexample, in an exemplary embodiment of the present invention the laserbeam 110 is protected by a laser shroud assembly 1901 which shields thebeam from the laser 120 to near the surface of the workpiece 115. Arepresentation of this can be seen in FIG. 19. The shroud 1901 (shown incross-section) protects the beam 110 from interference and providesadditional safety during operation. Furthermore, the shroud can becoupled to a fume extraction system 1903 which draws any welding fumesaway from the welding zone. Because embodiments can be utilized with noshielding gas the shroud 1901 can positioned very close to the weld todirectly draw the fumes away from the welding zone. In fact the shroud1901 can be positioned such that its distance Z above the weld is in therange of 0.125 to 0.5 inches. Of course, other distances can be used butcare must be taken not to disturb the weld puddle or to significantlydiminish the effectiveness of the shroud 1901. Because fume extractionsystems 1903 are generally understood and known in the welding industrytheir construction and operation will not be discussed in detail herein.Although FIG. 19 shows the shroud 1901 only protecting the beam 110, itis of course possible that the shroud 1901 be constructed such that itencompasses at least a portion of the wire 140 and contact tip 160. Forexample, it is possible that the bottom opening of the shroud 1901 belarge enough to cover nearly the entire weld puddle, or even be largerthan the weld puddle, to increase fume extraction.

In exemplary embodiments of the present invention used to weld coatedworkpieces, such as galvanized work pieces, a much less expensiveshielding gas may be employed. For example, a 100% CO₂ shielding gas canbe used for welding many different materials, including mild steels.This is also true when welding more complex metals, such as stainlesssteel, duplex steel and super duplex steel, which can be welded withonly a 100% nitrogen shielding gas. In typical arc welding operations,the welding of stainless steel, duplex steel or super-duplex steelrequires more complex mixtures of shielding gas, which can be quiteexpensive. Embodiments of the present invention allow these steels to bewelded with only a 100% nitrogen shielding gas. Further, otherembodiments can have these steels welded with no shielding. In a typicalwelding process for galvanized materials, a special mix shielding gasmust be utilized, such as an argon/CO₂ blend. This type of gas needs tobe used, in part, because during normal arc welding a cathode and anodeis present in the weld zone. However, as explained above and furtherexplained below, there is no welding arc and, as such, there is no anodeor cathode present in the weld zone. Therefore, the opportunity for thefiller metal to pick up harmful elements from the atmosphere is greatlyreduced, as there is no arc and no droplet transfer. It should be notedthat even though many embodiments of the present invention permitwelding without the use of shielding—like shielding gas—a gas flow canbe utilized over the weld to remove vapor or contaminates from the weldzone. That is, during welding it is contemplated that air, nitrogen,CO₂, or other gases, can be blown over the weld so as to removecontaminates from the weld zone.

In addition to be able to weld coated materials at high speeds,embodiments of the present invention can also be utilized to welddual-phase steels with a significantly reduced heat affected zone(“HAZ”). A dual-phase steel is a high strength steel having both aferrite and martensitic microstructure, thus allowing the steel to havehigh strength and good formability. Because of the nature of dual-phasesteels the strength of a dual phase steel weld is limited by thestrength of the heat affected zone. The heat affected zone is the zonearound the weld joint (not including the filler metal) which issignificantly heated from the welding process such that itsmicrostructure is adversely changed because of the arc welding process.In known arc welding processes the heat affected zone is quite largebecause of the size of the arc plasma and the high heat input into theweld zone. Because the heat affected zone is quite large the heataffected zone becomes the strength limiting portion of the weld. Assuch, arc welding processes typically use mild steel filler wires 140 toweld such joints (for example, ER70S-6, or -3 type electrodes) since theuse of high strength electrodes is unnecessary. Furthermore, because ofthis designers must locate welding joints in dual-phase steelsstrategically out of high stress structures—such as in automobileframes, bumpers, engine cradles, etc.

As discussed above the use of the laser device 120 provides high levelsof precision in the creation of the weld puddle. Because of thisprecision the heat affected zone surrounding the weld bead can be keptvery small, or the overall effect of the heat affected zone to theworkpiece can be minimized. In fact, in some embodiments the heataffected zone of the work piece can be nearly eliminated. This is doneby maintaining the focus of the laser beam 110 only on the portions ofthe workpiece in which a puddle is to be created. By significantlyreducing the size of the heat affected zone the strength of the basemetal is not compromised as much as if an arc welding process is used.As such, the presence or location of the heat affected zone is no longerthe limiting factor in the design of a welded structure. Embodiments ofthe present invention allow for the use of higher strength filler wiresbecause the composition and strength of the workpiece and the strengthof the filler wire can be the driving factors in a structural design,rather than the heat affected zone. For example, embodiments of thepresent invention now permit the use of electrodes having at least an 80ksi yield strength, such as ER80S-D2, type electrodes. Of course, thiselectrode is intended to be exemplary. Furthermore, because there isless overall heat input then from arc welding the cooling rates of thepuddle will be quicker, which means that the chemistry of the fillerwires used can be leaner but give equal or greater performance overexisting wire.

Additionally, exemplary embodiments of the present invention can be usedto weld titanium with significantly reduced shielding requirements. Itis known that when welding titanium with an arc welding process greatcare must be taken to ensure an acceptable weld is created. This isbecause during the welding process titanium has a strong affinity toreact with oxygen. The reaction between titanium and oxygen createstitanium dioxide, which if present in the weld pool may significantlyreduce the strength and/or ductility of the weld joint. Because of this,when arc welding titanium it is necessary to provide a significantamount of trailing shielding gas to shield not only the arc but thetrailing molten puddle from the atmosphere as the puddle cools. Becauseof the heat generated from arc welding the weld puddle can be quitelarge and remain molten for long periods of time, thus requiring asignificant amount of shielding gas. Embodiments of the presentinvention significantly reduce the time the material is molten andrapidly cools so the need for this extra shielding gas is reduced.

As explained above, the laser beam 110 can be focused very carefully tosignificantly reduce the overall heat input into the weld zone and thussignificantly reduce the size of the weld puddle. Because the weldpuddle is smaller the weld puddle cools much quicker. As such, there isno need for a trailing shielding gas, but only shielding at the weld.Further, for the similar reasons discussed above the spatter factor whenwelding titanium is greatly reduced while the rate of welding isincreased.

Turning now to FIGS. 7 and 7A, an open root type welding joint is shown.Open root joints are often used to weld thick plates and pipes and canoften occur in remote and environmentally difficult locations. There area number of known methods to weld open root joints, including shieldedmetal arc welding (SMAW), gas tungsten arc welding (GTAW), gas metal arcwelding (GMAW), flux cored arc welding (FCAW), submerged arc welding(SAW), and flux cored arc welding, self shielded (FCAW-S). These weldingprocesses have various disadvantages including the need for shielding,speed limitations, the creation of slag, etc.

Thus, embodiments of the present invention greatly improve theefficiencies and speeds at which these types of welds can be performed.Specifically, the use of shielding gas can be eliminated, or greatlyreduced, and the generation of slag can be completely eliminated.Furthermore, welding at high speeds can be obtained with minimal spatterand porosity.

FIGS. 7 and 7A show representative open root welding joints being weldedby exemplary embodiments of the present invention. Of course,embodiments of the present invention can be utilized to weld a widevariety of weld joints, not just lap or open root type joints. In FIG. 7a gap 705 is shown between the workpieces W1/W2 and each respectiveworkpiece has an angled surface 701/703, respectively. Just as discussedabove, embodiments of the present invention use a laser device 120 tocreate a precise molten puddle on the surfaces 701/703 and a pre-heatedfiller wire (not shown) is deposited into the puddles, respectively, asdescribed above.

In fact, exemplary embodiments of the present invention are not limitedto directing a single filler wire to each respective weld puddle.Because no welding arc is generated in the welding process describedherein, more than one filler wire can be directed to any one weldpuddle. By increasing the number of filler wires to a given weld puddlethe overall deposition rate of the weld process can be significantlyincreased without a significant increase in heat input. Thus, it iscontemplated that open root weld joints (such as the type shown in FIGS.7 and 7A) can be filled in a single weld pass.

Further, as shown in FIG. 7, in some exemplary embodiments of thepresent invention multiple laser beams 110 and 110A can be utilized tomelt more than one location in the weld joint at the same time. This canbe accomplished in a number of ways. In a first embodiment, shown inFIG. 7, a beam splitter 121 is utilized and coupled to the laser device120. A beam splitter 121 is known to those knowledgeable of laserdevices and need not be discussed in detail herein. The beam splitter121 splits the beam from the laser device 120 into two (or more)separate beams 110/110A and can direct them to two different surfaces.In such an embodiment multiple surfaces can be irradiated at the sametime, providing further precision and accuracy in welding. In anotherembodiment, each of the separate beams 110 and 110A can be created by aseparate laser device, such that each beam is emitted from its owndedicated device.

In such an embodiment, using multiple laser devices, many aspects of thewelding operation can be varied to adapt to different welding needs. Forexample, the beams generated by the separate laser devices can havedifferent energy densities; can have different shapes, and/or differentcross-sectional areas at the weld joint. With this flexibility, aspectsof the welding process can be modified and customized to fulfill anyspecific weld parameters needed. Of course, this can also beaccomplished with the utilization of a single laser device and a beamsplitter 121, but some of the flexibility may be limited with the use ofthe single laser source. Further, the present invention is not limitedto either a single or double laser configuration, as it is contemplatedthat any number of lasers can be used as desired.

In further exemplary embodiments, a beam scanning device can be used.Such devices are known in the laser or beam emitting arts and are usedto scan the beam 110 in a pattern over a surface of the workpiece. Withsuch devices the scan rates and patterns, as well as the dwell time, canbe used to heat the workpiece 115 in the desired fashion. Further, theoutput power of the energy source (e.g., laser) can be regulated asdesired to create the desired puddle formation. Additionally, the opticsemployed within the laser 120 can be optimized based on the desiredoperation and joint parameters. For example, line and integrator opticscan be utilized to produce a focused line beam for a wide welding orcladding operation or an integrator can be used to produce asquare/rectangular beam having a uniform power distribution.

FIG. 7A depicts another embodiment of the present invention, where asingle beam 110 is directed to the open root joint to melt the surfaces701/703.

Because of the precision of the laser beams 110 and 110A, the beams110/110A can be focused only on the surfaces 701/703 and away from thegap 705. Because of this, the melt-through (which would normally fallthrough the gap 705) can be controlled which greatly improves thecontrol of the back-side weld bead (the weld bead at the bottom surfaceof the gap 705).

In each of FIGS. 7 and 7A a gap 705 exists between the workpieces W1 andW2 which is filled with a weld bead 707. In an exemplary embodiment,this weld bead 705 is created by a laser device (not shown). Thus, forexample, during a welding operation a first laser device (not shown)directs a first laser beam (not shown) to the gap 705 to weld theworkpieces W1 and W2 together with the laser weld bead 707, while thesecond laser device 120 directs at least one laser beam 110/110A to thesurfaces 701/703 to create weld puddles where a filler wires(s) (notshown) is deposited to complete the weld. The gap weld bead 707 can becreated just by a laser, if the gap is small enough, or can be createdby the use of a laser and a filler wire if the gap 705 so requires.Specifically, it may be necessary to add filler metal to properly fillthe gap 705 and thus a filler wire should be used. The creation of thisgap bead 705 is similar to that described above with regard to variousexemplary embodiments of the present invention.

It should be noted that the high intensity energy sources, such as thelaser devices 120 discussed herein, should be of a type havingsufficient power to provide the necessary energy density for the desiredwelding operation. That is, the laser device 120 should have a powersufficient to create and maintain a stable weld puddle throughout thewelding process, and also reach the desired weld penetration. Forexample, for some applications lasers should have the ability to“keyhole” the workpieces being welded. This means that the laser shouldhave sufficient power to fully penetrate the workpiece, whilemaintaining that level of penetration as the laser travels along theworkpiece. Exemplary lasers should have power capabilities in the rangeof 1 to 20 kW, and may have a power capability in the range of 5 to 20kW. Higher power lasers can be utilized, but can become very costly. Ofcourse, it is noted that the use of the beam splitter 121 or multiplelasers can be used in other types of weld joints as well, and can beused in lap joints such as those shown in FIGS. 6 and 6A.

FIG. 7B depicts another exemplary embodiment of the present invention.In this embodiment a narrow groove, deep open root joint is shown. Whenarc welding deep joints (greater than 1 inch in depth) it can bedifficult to weld the bottom of the joint when the gap G for the grooveis narrow. This is because it is difficult to effectively delivershielding gas into such a deep groove and the narrow walls of the groovecan cause interference with the stability of a welding arc. Because theworkpiece is typically a ferrous material the walls of the joint caninterfere, magnetically, with the welding arc. Because of this, whenusing typical arc welding procedures the gap G of the groove needs to besufficiently wide so that the arc remains stable. However, the wider thegroove the more filler metal is needed to complete the weld. Becauseembodiments of the present invention do not require a shielding gas anddo not use a welding arc these issues are minimized. This allowsembodiments of the present invention to weld deep, narrow groovesefficiently and effectively. For example, in an exemplary embodiment ofthe present invention where the workpiece 115 has a thickness greaterthan 1 inch, the gap width G is in the range of 1.5 to 2 times thediameter of the filler wire 140 and the sidewall angle is in the rangeof 0.5 to 10 degrees. In an exemplary embodiment, the root passpreparation of such a weld joint can have a gap RG in the range of 1 to3 mm with a land in the range of 1/16 to ¼ inch. Thus, deep open rootjoints can be welded faster and with much less filler material thennormal arc welding processes. Further, because aspects of the presentinvention introduce much less heat into the welding zone, the tip 160can be designed to facilitate much closer delivery to the weld puddle toavoid contact with the side wall. That is, the tip 160 can be madesmaller and constructed as an insulated guide with a narrow structure.In a further exemplary embodiment, a translation device or mechanism canbe used to move the laser and wire across the width of the weld to weldboth sides of the joint at the same time.

As shown in FIG. 8 a butt-type joint can be welded with embodiments ofthe present invention. In FIG. 8 a flush butt-type joint is shown,however it is contemplated that butt-type joints with v-notch groves onthe upper and bottom surfaces of the weld joint can be also welded. Inthe embodiment shown in FIG. 8, two laser devices 120 and 120A are shownon either side of the weld joint, each respectively creating their ownweld puddle 801 and 803. Like FIGS. 7 and 7A the heated filler wires arenot shown as they are trailing behind the laser beams 110/110A in theview shown.

When welding butt-type joints with known arc technology there can besignificant problems with “arc blow”, which occurs when the magneticfields generated by welding arcs interfere with each other such that thearcs cause each other to move erratically. Further, when two or more arcwelding systems are being used to weld on a the same weld joint therecan be significant issues caused by the interference of the respectivewelding currents. Additionally, because of the depth of penetration ofarc welding methods, due to—in part—the high heat input, the thicknessesof the workpieces that can be welded with arcs on either side of theweld joint are limited. That is, such welding cannot be done on thinworkpieces.

When welding with embodiments of the present invention, these issues areeliminated. Because there is no welding arc being utilized there is noarc blow interference or welding current interference issues. Further,because of the precise control in heat input and depth of penetrationwhich is capable through the use of lasers, much thinner workpieces canbe welded on both sides of the weld joint at the same time.

A further exemplary embodiment of the present invention is shown in FIG.9. In this embodiment two laser beams 110 and 110A are utilized—in linewith each other—to create a unique weld profile. In the embodiment showna first beam 110 (emitted from a first laser device 120) is used tocreate first portion of a weld puddle 901 having a first cross-sectionalarea and depth, while the second beam 110A (emitted from a second laserdevice—not shown) is used to create a second portion of a weld puddle903 having a second cross-sectional area and depth, which is differentfrom the first. This embodiment can be used when it is desirable to havea portion of the weld bead having a deeper depth of penetration than theremainder of the weld bead. For example, as shown in FIG. 9 the puddle901 is made deeper and narrower than the weld puddle 903 which is madewider and shallower. Such an embodiment can be used when a deeppenetration level is needed where the work pieces meet but is notdesired for the entire portion of the weld joint.

In a further exemplary embodiment of the present invention, the firstpuddle 903 can be the weld puddle which creates the weld for the joint.This first puddle/joint is created with a first laser 120 and a fillerwire (not shown), and is made to appropriate depth of penetration. Afterthis weld joint is made a second laser (not shown) emitting a secondlaser beam 110A passes over the joint to create a second puddle 903 witha different profile where this second puddle is used to deposit anoverlay of some kind as discussed with the embodiments above. Thisoverlay will be deposited using a second filler wire, having a differentchemistry than the first filler wire. For example, embodiments of thisinvention can be used to place a corrosion resistant cladding layer overthe weld joint shortly or immediately after the joint is welded. Thiswelding operation can also be accomplished with a single laser device120 where the beam 110 is oscillated between a first beam shape/densityand a second beam shape/density to provide the desired weld puddleprofile. Thus, it is not necessary for multiple laser devices to beemployed.

As explained above, a corrosion resistant coating on the workpieces(such as galvanization), is removed during the welding process. Howeverit may be desirable to have the weld joint coated again for corrosionresistance purposes and so the second beam 110A and laser can be used toadd a corrosion resistant overlay 903, such as a cladding layer, on topof the joint 901.

Because of the various advantages of the present invention, it is alsopossible to easily join dissimilar metals via a welding operation.Joining dissimilar metals with an arc welding process is difficult usingan arc welding process because the dissimilar materials and the requiredchemistries for a filler material can lead to cracking and inferiorwelds. This is particularly true when attempting to arc weld aluminumand steel together, which have very different melting temperatures, orwhen trying weld stainless steels to mild steel, because of theirdifferent chemistries. However, with embodiments of the presentinvention, such issues are mitigated.

FIG. 10 depicts an exemplary embodiment of this invention. Although aV-type joint is shown, the present invention is not limited in thisregard. In FIG. 10 two dissimilar metals are shown being joined at aweld joint 1000. In this example, the two dissimilar metals are aluminumand steel. In this exemplary embodiment, two different laser sources1010 and 1020 are employed. However, two laser devices are not requiredin all embodiments as a single device can be oscillated to provide thenecessary energy to melt the two different materials—this will bediscussed further below. Laser 1010 emits the beam 1011 which isdirected at the steel workpiece and the laser 1020 emits the beam 1021at the aluminum workpiece. Because each of the respective workpieces ismade from different metals or alloys they have different meltingtemperatures. As such, each of the respective laser beams 1011/1021 hasdifferent energy densities at the weld puddles 1012 and 1022. Because ofthe differing energy densities each of the respective weld puddles 1012and 1022 can be maintained at the proper size and depth. This alsoprevents excessive penetration and heat input in the workpiece with thelower melting temperature—for example, aluminum. In some embodiments,because of at least the weld joint, there is no need to have twoseparate, discrete weld puddles (as shown in FIG. 10), rather a singleweld puddle can be formed with both work pieces, where the meltedportions of each of the workpieces form a single weld puddle. Further,if the work pieces have different chemistries but have similar meltingtemperatures, it is possible to use a single beam to irradiate both workpieces at the same time, with the understanding that one work piece willmelt more than the other. Further, as briefly described above, it ispossible to use a single energy source (like laser device 120) toirradiate both work pieces. For example, a laser device 120 could use afirst beam shape and/or energy density to melt the first work piece andthen oscillate/change to a second beam shape and/or energy density tomelt the second work piece. The oscillation and changing of the beamcharacteristics should be accomplished at a sufficient rate to ensurethat proper melting of both work pieces is maintained so that the weldpuddle(s) are kept stable and consistent during the welding process.Other single beam embodiments can utilize a beam 110 having a shapewhich provides more heat input into one workpiece over the other toensure sufficient melting of each workpiece. In such embodiments theenergy density of the beam can be uniform for the cross-section of thebeam. For example, the beam 110 can have a trapezoidal or triangularshape so that the overall heat input into one workpiece will be lessthan other, because of the shape of the beam. Alternatively, someembodiments can use a beam 110 having a non-uniform energy distributionin its cross-section. For example, the beam 110 can have a rectangularshape (such that it impacts both workpieces) but a first region of thebeam will have a first energy density and a second region of the beam110 will have a second energy density which is different than the firstregion, so each of the regions can appropriately melt the respectiveworkpieces. As an example, the beam 110 can have a first region with ahigh energy density to melt a steel workpiece while the second regionwill have a lower energy density to melt an aluminum workpiece.

In FIG. 10 two filler wires 1030 and 1030A are shown, each beingdirected to a weld puddle 1012 and 1022, respectively. Although theembodiment shown in FIG. 10 is employing two filler wires, the presentinvention is not limited in this regard. As discussed above with respectto other embodiments, it is contemplated that only one filler wire canbe used, or more than two wires can be used, depending on the desiredweld parameters, such as the desired bead shape and deposition rate.When a single wire is employed it can be directed to either a commonpuddle (formed from the melted portions of both of the workpieces), orthe wire can be directed to only one of melted portions for integrationinto the weld joint. Thus, for example, in the embodiment shown in FIG.10 a wire can be directed to the melted portion 1022 which will then becombined with the melted portion 1012 for formation of the weld joint.Of course, if a single wire is employed it should be heated to atemperature to allow the wire to melt in the portion 1022/1012 intowhich it is being immersed.

Because dissimilar metals are being joined the chemistry of the fillerwires should be chosen to ensure that the wires can sufficiently bondwith the metals being joined. Furthermore, the composition of the fillerwire(s) should be chosen such that it has a suitable melt temperature,which allows it to melt and be consumed in the weld puddle of the lowertemperature weld puddle. In fact, it is contemplated that thechemistries of the multiple filler wires can be different to attain theproper weld chemistry. This is particularly the case when the twodifferent workpieces have material compositions where minimal admixturewill occur between the materials. In FIG. 10, the lower temperature weldpuddle is the aluminum weld puddle 1012, and as such the filler wire(s)1030(A) are formulated so as to melt at a similar temperature so thatthey can be easily consumed in the puddle 1012. In the example above,using aluminum and steel work pieces, the filler wires can be siliconbronze, nickel aluminum bronze or aluminum bronze based wire having amelting temperature similar to that of the workpiece. Of course, it iscontemplated that the filler wire compositions should be chosen to matchthe desired mechanical and welding performance properties, while at thesame time providing melting characteristics which are similar to that ofthe at least one of the workpieces to be welded.

FIGS. 11A through 11C depict various embodiments of the tip 160 that canbe employed. FIG. 11A depicts a tip 160 which is very similar inconstruction and operation to that of a normal arc welding contact tip.During hot wire welding as described herein the heating current isdirected to the contact tip 160 from the power supply 170 and is passedfrom the tip 160 into the wire 140. The current is then directed throughthe wire to the workpiece via the contact of the wire 140 to theworkpiece W. This flow of current heats the wire 140 as describedherein. Of course, the power supply 170 may not be directly coupled tothe contact tip as shown but may be coupled to a wire feeder 150 whichdirects the current to the tip 160. FIG. 11B shows another embodiment ofthe present invention, where the tip 160 is comprised of two components160 and 160′, such that the negative terminal of the power supply 170 iscoupled to the second component 160′. In such an embodiment the heatingcurrent flows from the first tip component 160 to the wire 140 and theninto the second tip components 160′. The flow of the current through thewire 140, between the components 160 and 160′ causes the wire to heat asdescribed herein. FIG. 11C depicts another exemplary embodiment wherethe tip 160 contains an induction coil 1110, which causes the tip 160and the wire 140 to be heated via induction heating. In such anembodiment, the induction coil 1110 can be made integral with thecontact tip 160 or can be coiled around a surface of the tip 160. Ofcourse, other configurations can be used for the tip 160 so long as thetip deliveries the needed heating current/power to the wire 140 so thatthe wire can achieve the desired temperature for the welding operation.

The operation of exemplary embodiments of the present invention will bedescribed. As discussed above, embodiments of the present inventionemploy both a high intensity energy source and a power supply whichheats the filler wire. Each aspect of this process will be discussed inturn. It is noted that the following descriptions and discussions arenot intended to supplant or replace any of the discussions providedpreviously with respect to the previously discussed overlayingembodiments, but are intended to supplement those discussions relativeto welding or joining applications. The discussions previously regardingoverlaying operations are incorporated also for purposes of joining andwelding.

Exemplary embodiments for joining/welding can be similar to that shownin FIG. 1. As described above a hot wire power supply 170 is providedwhich provides a heating current to the filler wire 140. The currentpass from the contact tip 160 (which can be of any known construction)to the wire 140 and then into the workpiece. This resistance heatingcurrent causes the wire 140 between the tip 160 and the workpiece toreach a temperature at or near the melting temperature of the fillerwire 140 being employed. Of course, the melting temperature of thefiller wire 140 will vary depending on the size and chemistry of thewire 140. Accordingly, the desired temperature of the filler wire duringwelding will vary depending on the wire 140. As will be furtherdiscussed below, the desired operating temperature for the filler wirecan be a data input into the welding system so that the desired wiretemperature is maintained during welding. In any event, the temperatureof the wire should be such that the wire is consumed into the weldpuddle during the welding operation. In exemplary embodiments, at leasta portion of the filler wire 140 is solid as the wire enters the weldpuddle. For example, at least 30% of the filler wire is solid as thefiller wire enters the weld puddle.

In an exemplary embodiment of the present invention, the hot wire powersupply 170 supplies a current which maintains at least a portion of thefiller wire at a temperature at or above 75% of its melting temperature.For example, when using a mild steel filler wire 140 the temperature ofthe wire before it enters the puddle can be approximately 1,600° F.,whereas the wire has a melting temperature of about 2,000° F. Of course,it is understood that the respective melting temperatures and desiredoperational temperatures will varying on at least the alloy,composition, diameter and feed rate of the filler wire. In anotherexemplary embodiment, the power supply 170 maintains a portion of thefiller wire at a temperature at or above 90% of its melting temperature.In further exemplary embodiments, portions of the wire are maintained ata temperature of the wire which is at or above 95% of its meltingtemperature. In exemplary embodiments, the wire 140 will have atemperature gradient from the point at which the heating current isimparted to the wire 140 and the puddle, where the temperature at thepuddle is higher than that at the input point of the heating current. Itis desirable to have the hottest temperature of the wire 140 at or nearthe point at which the wire enters the puddle to facilitate efficientmelting of the wire 140. Thus, the temperature percentages stated aboveare to be measured on the wire at or near the point at which the wiresenters the puddle. By maintaining the filler wire 140 at a temperatureclose to or at its melting temperature the wire 140 is easily meltedinto or consumed into the weld puddle created by the heat source/laser120. That is, the wire 140 is of a temperature which does not result insignificantly quenching the weld puddle when the wire 140 makes contactwith the puddle. Because of the high temperature of the wire 140 thewire melts quickly when it makes contact with the weld puddle. It isdesirable to have the wire temperature such that the wire does notbottom out in the weld pool—make contact with the non-melted portion ofthe weld pool. Such contact can adversely affect the quality of theweld.

As described previously, in some exemplary embodiments, the completemelting of the wire 140 can be facilitated only by entry of the wire 140into the puddle. However, in other exemplary embodiments the wire 140can be completely melted by a combination of the puddle and the laserbeam 110 impacting on a portion of the wire 140. In yet otherembodiments of the present invention, the heating/melting of the wire140 can be aided by the laser beam 110 such that the beam 110contributes to the heating of the wire 140. However, because many fillerwires 140 are made of materials which can be reflective, if a reflectivelaser type is used the wire 140 should be heated to a temperature suchthat its surface reflectivity is reduced, allowing the beam 110 tocontribute to the heating/melting of the wire 140. In exemplaryembodiments of this configuration, the wire 140 and beam 110 intersectat the point at which the wire 140 enters the puddle.

As also discussed previously with regard to FIG. 1, the power supply 170and the controller 195 control the heating current to the wire 140 suchthat, during welding, the wire 140 maintains contact with the workpieceand no arc is generated. Contrary to arc welding technology, thepresence of an arc when welding with embodiments of the presentinvention can result in significant weld deficiencies. Thus, in someembodiments (as those discussed above) the voltage between the wire 140and the weld puddle should be maintained at or near 0 volts—whichindicates that the wire is shorted to or in contact with theworkpiece/weld puddle.

However, in other exemplary embodiments of the present invention it ispossible to provide a current at such a level so that a voltage levelabove 0 volts is attained without an arc being created. By utilizinghigher currents values it is possible to maintain the electrode 140 attemperatures at a higher level and closer to an electrode's meltingtemperature. This allows the welding process to proceed faster. Inexemplary embodiments of the present invention, the power supply 170monitors the voltage and as the voltage reaches or approaches a voltagevalue at some point above 0 volts the power supply 170 stops flowingcurrent to the wire 140 to ensure that no arc is created. The voltagethreshold level will typically vary, at least in part, due to the typeof welding electrode 140 being used. For example, in some exemplaryembodiments of the present invention the threshold voltage level is ator below 6 volts. In another exemplary embodiment, the threshold levelis at or below 9 volts. In a further exemplary embodiment, the thresholdlevel is at or below 14 volts, and in an additional exemplaryembodiment; the threshold level is at or below 16 volts. For example,when using mild steel filler wires the threshold level for voltage willbe of the lower type, while filler wires which are for stainless steelwelding can handle the higher voltage before an arc is created.

In further exemplary embodiments, rather than maintaining a voltagelevel below a threshold, such as above, the voltage is maintained in anoperational range. In such an embodiment, it is desirable to maintainthe voltage above a minimum amount—ensuring a high enough current tomaintain the filler wire at or near its melting temperature but below avoltage level such that no welding arc is created. For example, thevoltage can be maintained in a range of 1 to 16 volts. In a furtherexemplary embodiment the voltage is maintained in a range of 6 to 9volts. In another example, the voltage can be maintained between 12 and16 volts. Of course, the desired operational range can be affected bythe filler wire 140 used for the welding operation, such that a range(or threshold) used for a welding operation is selected, at least inpart, based on the filler wire used or characteristics of the fillerwire used. In utilizing such a range the bottom of the range is set to avoltage at which the filler wire can be sufficiently consumed in theweld puddle and the upper limit of the range is set to a voltage suchthat the creation of an arc is avoided.

As described previously, as the voltage exceeds a desired thresholdvoltage the heating current is shut off by the power supply 170 suchthat no arc is created. This aspect of the present invention will bediscussed further below.

In the many embodiments described above the power supply 170 containscircuitry which is utilized to monitor and maintain the voltage asdescribed above. The construction of such type of circuitry is known tothose in the industry. However, traditionally such circuitry has beenutilized to maintain voltage above a certain threshold for arc welding.

In further exemplary embodiments, the heating current can also bemonitored and/or regulated by the power supply 170. This can be done inaddition to monitoring voltage, power, or some level of avoltage/amperage characteristic as an alternative. That is, the currentcan be maintained at a desired level or levels to ensure that the wire140 is maintained at an appropriate temperature—for proper consumptionin the weld puddle, but yet below an arc generation current level. Forexample, in such an embodiment the voltage and/or the current are beingmonitored to ensure that either one or both are within a specified rangeor below a desired threshold. The power supply then regulates thecurrent supplied to ensure that no arc is created but the desiredoperational parameters are maintained.

In yet a further exemplary embodiment of the present invention, theheating power (V×I) can also be monitored and regulated by the powersupply 170. Specifically, in such embodiments the voltage and currentfor the heating power is monitored to be maintained at a desired level,or in a desired range. Thus, the power supply not only regulates thevoltage or current to the wire, but can regulate both the current andthe voltage. Such an embodiment may provide improved control over thewelding system. In such embodiments the heating power to the wire can beset to an upper threshold level or an optimal operational range suchthat the power is to be maintained either below the threshold level orwithin the desired range (similar to that discussed above regarding thevoltage). Again, the threshold or range settings will be based oncharacteristics of the filler wire and welding being performed, and canbe based—at least in part—on the filler wire selected. For example, itmay be determined that an optimal power setting for a mild steelelectrode having a diameter of 0.045″ is in the range of 1950 to 2,050watts. The power supply will regulate the voltage and current such thatthe power remains in this operational range. Similarly, if the powerthreshold is set at 2,000 watts, the power supply will regulate thevoltage and current so that the power level does not exceed but is closeto this threshold.

In further exemplary embodiments of the present invention, the powersupply 170 contains circuits which monitor the rate of change of theheating voltage (dv/dt), current (di/dt), and or power (dp/dt). Suchcircuits are often called premonition circuits and their generalconstruction is known. In such embodiments, the rate of change of thevoltage, current and/or power is monitored such that if the rate ofchange exceeds a certain threshold the heating current to the wire 140is turned off.

In an exemplary embodiment of the present invention, the change ofresistance (dr/dt) is also monitored. In such an embodiment, theresistance in the wire between the contact tip and the puddle ismonitored. During welding, as the wire heats up it starts to neck downand has a tendency to form an arc, during which time the resistance inthe wire increases exponentially. When this increase is detected theoutput of the power supply is turned off as described herein to ensurean arc is not created. Embodiments regulate the voltage, current, orboth, to ensure that the resistance in the wire is maintained at adesired level.

In further exemplary embodiments of the present invention, rather thanshutting off the heating current when the threshold level is detected,the power supply 170 reduces the heating current to a non-arc generationlevel. Such a level can be a background current level where no arc willbe generated if the wire is separated from the weld puddle. For example,an exemplary embodiment of the present invention can have a non-arcgeneration current level of 50 amps, where once an arc generation isdetected or predicted, or an upper threshold (discussed above) isreached, the power supply 170 drops the heating current from itsoperating level to the non-arc generation level for either apredetermined amount of time (for example, 1 to 10 ms) or until thedetected voltage, current, power, and/or resistance drops below theupper threshold. This non-arc generation threshold can be a voltagelevel, current level, resistance level, and/or a power level. In suchembodiments, by maintaining a current output during an arc generationevent—albeit at a low level—it can cause a quicker recovery to theheating current operational level.

In another exemplary embodiment of the present invention, the output ofthe power supply 170 is controlled such that no substantial arc iscreated during the welding operation. In some exemplary weldingoperations the power supply can be controlled such that no substantialarc is created between the filler wire 140 and the puddle. It isgenerally known that an arc is created between a physical gap betweenthe distal end of the filler wire 140 and the weld puddle. As describedabove, exemplary embodiments of the present invention prevent this arcfrom being created by keeping the filler wire 140 in contact with thepuddle. However, in some exemplary embodiments the presence of aninsubstantial arc will not compromise the quality of the weld. That is,in some exemplary welding operations the creation of an insubstantialarc of a short duration will not result in a level of heat input thatwill compromise the weld quality. In such embodiments, the weldingsystem and power supply is controlled and operated as described hereinwith respect to avoiding an arc completely, but the power supply 170 iscontrolled such that to the extent an arc is created the arc isinsubstantial. In some exemplary embodiments, the power supply 170 isoperated such that a created arc has a duration of less than 10 ms. Inother exemplary embodiments the arc has a duration of less than 1 ms,and in other exemplary embodiments the arc has a duration of less than300 μs. In such embodiments, the existence of such arcs does notcompromise the weld quality because the arc does not impart substantialheat input into the weld or cause significant spatter or porosity. Thus,in such embodiments the power supply 170 is controlled such that to theextent an arc is created it is kept insubstantial in duration so thatthe weld quality is not compromised. The same control logic andcomponents as discussed herein with respect to other embodiments can beused in these exemplary embodiments. However, for the upper thresholdlimit the power supply 170 can use the detection of the creation of anarc, rather than a threshold point (of current, power, voltage,resistance) below a predetermined or predicted arc creation point. Suchan embodiment can allow the welding operation to operate closer to itslimits.

Because the filler wire 140 is desired to be in a constantly shortedstate (in constant contact with the weld puddle) the current tends todecay at a slow rate. This is because of the inductance present in thepower supply, welding cables and workpiece. In some applications, it maybe necessary to force the current to decay at a faster rate such thatthe current in the wire is reduced at a high rate. Generally, the fasterthe current can be reduced the better control over the joining methodwill be achieved. In an exemplary embodiment of the present invention,the ramp down time for the current, after detection of a threshold beingreached or exceeded, is 1 millisecond. In another exemplary embodimentof the present invention, the ramp down time for the current is 300microseconds or less. In another exemplary embodiment, the ramp downtime is in the range of 300 to 100 microseconds.

In an exemplary embodiment, to achieve such ramp down times, a ramp downcircuit is introduced into the power supply 170 which aids in reducingthe ramp down time when an arc is predicted or detected. For example,when an arc is either detected or predicted a ramp down circuit opens upwhich introduces resistance into the circuit. For example, theresistance can be of a type which reduces the flow of current to below50 amps in 50 microseconds. A simplified example of such a circuit isshown in FIG. 18. The circuit 1800 has a resistor 1801 and a switch 1803placed into the welding circuit such that when the power supply isoperating and providing current the switch 1803 is closed. However, whenthe power supply stops supplying power (to prevent the creation of anarc or when an arc is detected) the switch opens forcing the inducedcurrent through the resistor 1801. The resistor 1801 greatly increasesthe resistance of the circuit and reduces the current at a quicker pace.Such a circuit type is generally known in the welding industry can befound a Power Wave® welding power supply manufactured by The LincolnElectric Company, of Cleveland, Ohio, which incorporatessurface-tension-transfer technology (“STT”). STT technology is generallydescribed in U.S. Pat. Nos. 4,866,247, 5,148,001, 6,051,810 and7,109,439, which are incorporated herein by reference in their entirety.Of course, these patents generally discuss using the disclosed circuitryto ensure that an arc is created and maintained—those skilled in theindustry can easily adapt such a system to ensure that no arc iscreated.

The above discussion can be further understood with reference to FIG.12, in which an exemplary welding system is depicted. (It should benoted that the laser system is not shown for clarity). The system 1200is shown having a hot wire power supply 1210 (which can be of a typesimilar to that shown as 170 in FIG. 1). The power supply 1210 can be ofa known welding power supply construction, such as an inverter-typepower supply. Because the design, operation and construction of suchpower supplies are known they will not be discussed in detail herein.The power supply 1210 contains a user input 1220 which allows a user toinput data including, but not limited to, wire feed speed, wire type,wire diameter, a desired power level, a desired wire temperature,voltage and/or current level. Of course, other input parameters can beutilized as needed. The user interface 1220 is coupled to aCPU/controller 1230 which receives the user input data and uses thisinformation to create the needed operational set points or ranges forthe power module 1250. The power module 1250 can be of any known type orconstruction, including an inverter or transformer type module.

The CPU/controller 1230 can determine the desired operational parametersin any number of ways, including using a lookup table, In such anembodiment, the CPU/controller 1230 utilizes the input data, forexample, wire feed speed, wire diameter and wire type to determine thedesired current level for the output (to appropriately heat the wire140) and the threshold voltage or power level (or the acceptableoperating range of voltage or power). This is because the needed currentto heat the wire 140 to the appropriate temperature will be based on atleast the input parameters. That is, an aluminum wire 140 may have alower melting temperature than a mild steel electrode, and thus requiresless current/power to melt the wire 140. Additionally, a smallerdiameter wire 140 will require less current/power than a larger diameterelectrode. Also, as the wire feed speed increases (and accordingly thedeposition rate) the needed current/power level to melt the wire will behigher.

Similarly, the input data will be used by the CPU/controller 1230 todetermine the voltage/power thresholds and/or ranges (e.g., power,current, and/or voltage) for operation such that the creation of an arcis avoided. For example, for a mild steel electrode having a diameter of0.045 inches can have a voltage range setting of 6 to 9 volts, where thepower module 1250 is driven to maintain the voltage between 6 to 9volts. In such an embodiment, the current, voltage, and/or power aredriven to maintain a minimum of 6 volts—which ensures that thecurrent/power is sufficiently high to appropriately heat theelectrode—and keep the voltage at or below 9 volts to ensure that no arcis created and that a melting temperature of the wire 140 is notexceeded. Of course, other set point parameters, such as voltage,current, power, or resistance rate changes can also be set by theCPU/controller 1230 as desired.

As shown, a positive terminal 1221 of the power supply 1210 is coupledto the contact tip 160 of the hot wire system and a negative terminal ofthe power supply is coupled to the workpiece W. Thus, a heating currentis supplied through the positive terminal 1221 to the wire 140 andreturned through the negative terminal 1222. Such a configuration isgenerally known.

Of course, in another exemplary embodiment the negative terminal 1222can also be connected to the tip 160. Since resistance heating can beused to heat the wire 140, the tip can be of a construction (as shown inFIG. 11) where both the negative and positive terminals 1221/1222 can becoupled to the contact tip 140 to heat the wire 140. For example, thecontact tip 160 can have a dual construction (as shown in FIG. 11B) oruse an induction coil (as shown in FIG. 11C).

A feedback sense lead 1223 is also coupled to the power supply 1210.This feedback sense lead can monitor voltage and deliver the detectedvoltage to a voltage detection circuit 1240. The voltage detectioncircuit 1240 communicates the detected voltage and/or detected voltagerate of change to the CPU/controller 1230 which controls the operationof the module 1250 accordingly. For example, if the voltage detected isbelow a desired operational range, the CPU/controller 1230 instructs themodule 1250 to increase its output (current, voltage, and/or power)until the detected voltage is within the desired operational range.Similarly, if the detected voltage is at or above a desired thresholdthe CPU/controller 1230 instructs the module 1250 to shut off the flowof current to the tip 160 so that an arc is not created. If the voltagedrops below the desired threshold the CPU/controller 1230 instructs themodule 1250 to supply a current or voltage, or both to continue thewelding process. Of course, the CPU/controller 1230 can also instructthe module 1250 to maintain or supply a desired power level.

It is noted that the detection circuit 1240 and CPU/controller 1230 canhave a similar construction and operation as the controller 195 shown inFIG. 1. In exemplary embodiments of the present invention, thesampling/detection rate is at least 10 KHz. In other exemplaryembodiments, the detection/sampling rate is in the range of 100 to 200KHz.

FIGS. 13A-C depict exemplary current and voltage waveforms utilized inembodiments of the present invention. Each of these waveforms will bediscussed in turn. FIG. 13A shows the voltage and current waveforms foran embodiment where the filler wire 140 touches the weld puddle afterthe power supply output is turned back on—after an arc detection event.As shown, the output voltage of the power supply was at some operationallevel below a determined threshold (9 volts) and then increases to thisthreshold during welding. The operational level can be a determinedlevel based on various input parameters (discussed previously) and canbe a set operational voltage, current and/or power level. Thisoperational level is the desired output of the power supply 170 for agiven welding operation and is to provide the desired heating signal tothe filler wire 140. During welding, an event may occur which can leadto the creation of an arc. In FIG. 13A the event causes an increase inthe voltage, causing it to increase to point A. At point A the powersupply/control circuitry hits the 9 volt threshold (which can be an arcdetection point or simply a predetermined upper threshold, which can bebelow an arc creation point) and turns off the output of the powersupply causing the current and voltage to drop to a reduced level atpoint B. The slope of the current drop can be controlled by theinclusion of a ramp down circuit (as discussed herein) which aids inrapidly reducing the current resultant from the system inductance. Thecurrent or voltage levels at point B can be predetermined or they can bereached after a predetermined duration in time. For example, in someembodiments, not only is an upper threshold for voltage (or current orpower) set for welding, but also a lower non-arc generation level. Thislower level can be either a lower voltage, current, or power level atwhich it is ensured that no arc can be created such that it isacceptable to turn back on the power supply and no arc will be created.Having such a lower level allows the power supply to turn back onquickly and ensure that no arc is created. For example, if a powersupply set point for welding is set at 2,000 watts, with a voltagethreshold of 11 volts, this lower power setting can be set at 500 watts.Thus, when the upper voltage threshold (which can also be a current orpower threshold depending on the embodiment) is reached the output isreduced to 500 watts. (This lower threshold can also be a lower currentor voltage setting, or both, as well). Alternatively, rather thansetting a lower detection limit a timing circuit can be utilized to turnbegin supplying current after a set duration of time. In exemplaryembodiments of the present invention, such duration can be in the rangeof 500 to 1000 ms. In FIG. 13A, point C represents the time the outputis again being supplied to the wire 140. It is noted that the delayshown between point B and C can be the result of an intentional delay orcan simply be a result of system delay. At point C current is againbeing supplied to heat the filler wire. However, because the filler wireis not yet touching the weld puddle the voltage increases while thecurrent does not. At point D the wire makes contact with the puddle andthe voltage and current settle back to the desired operational levels.As shown, the voltage may exceed the upper threshold prior to contact atD, which can occur when the power source has an OCV level higher thanthat of the operating threshold. For example, this higher OCV level canbe an upper limit set in the power supply as a result of its design ormanufacture.

FIG. 13B is similar to that described above, except that the filler wire140 is contacting the weld puddle when the output of the power supply isincreased. In such a situation either the wire never left the weldpuddle or the wire was contacted with the weld puddle prior to point C.FIG. 13B shows points C and D together because the wire is in contactwith the puddle when the output is turned back on. Thus both the currentand voltage increase to the desired operational setting at point E.

FIG. 13C is an embodiment where there is little or no delay between theoutput being turned off (point A) and being turned back on (point B),and the wire is in contact with the puddle some time prior to point B.The depicted waveforms can be utilized in embodiments described abovewhere a lower threshold is set such that when the lower threshold isreached—whether it's current, power, or voltage—the output is turnedback on with little or no delay. It is noted that this lower thresholdsetting can be set using the same or similar parameters as theoperational upper thresholds or ranges as described herein. For example,this lower threshold can be set based on wire composition, diameter,feed speed, or various other parameters described herein. Such anembodiment can minimize delay in returning to the desired operationalset points for welding and can minimize any necking that may occur inthe wire. The minimization of necking aids in minimizing the chances ofan arc being created.

FIG. 14 depicts yet another exemplary embodiment of the presentinvention. FIG. 14 shows an embodiment similar to that as shown inFIG. 1. However, certain components and connections are not depicted forclarity. FIG. 14 depicts a system 1400 in which a thermal sensor 1410 isutilized to monitor the temperature of the wire 140. The thermal sensor1410 can be of any known type capable of detecting the temperature ofthe wire 140. The sensor 1410 can make contact with the wire 140 or canbe coupled to the tip 160 so as to detect the temperature of the wire.In a further exemplary embodiment of the present invention, the sensor1410 is a type which uses a laser or infrared beam which is capable ofdetecting the temperature of a small object—such as the diameter of afiller wire—without contacting the wire 140. In such an embodiment thesensor 1410 is positioned such that the temperature of the wire 140 canbe detected at the stick out of the wire 140—that is at some pointbetween the end of the tip 160 and the weld puddle. The sensor 1410should also be positioned such that the sensor 1410 for the wire 140does not sense the weld puddle temperature.

The sensor 1410 is coupled to the sensing and control unit 195(discussed with regard to FIG. 1) such that temperature feed backinformation can be provided to the power supply 170 and/or the laserpower supply 130 so that the control of the system 1400 can beoptimized. For example, the power or current output of the power supply170 can be adjusted based on at least the feedback from the sensor 1410.That is, in an embodiment of the present invention either the user caninput a desired temperature setting (for a given weld and/or wire 140)or the sensing and control unit can set a desired temperature based onother user input data (wire feed speed, electrode type, etc.) and thenthe sensing and control unit 195 would control at least the power supply170 to maintain that desired temperature.

In such an embodiment it is possible to account for heating of the wire140 that may occur due to the laser beam 110 impacting on the wire 140before the wire enters the weld puddle. In embodiments of the inventionthe temperature of the wire 140 can be controlled only via power supply170 by controlling the current in the wire 140. However, in otherembodiments at least some of the heating of the wire 140 can come fromthe laser beam 110 impinging on at least a part of the wire 140. Assuch, the current or power from the power supply 170 alone may not berepresentative of the temperature of the wire 140. As such, utilizationof the sensor 1410 can aid in regulating the temperature of the wire 140through control of the power supply 170 and/or the laser power supply130.

In a further exemplary embodiment (also shown in FIG. 14) a temperaturesensor 1420 is directed to sense the temperature of the weld puddle. Inthis embodiment the temperature of the weld puddle is also coupled tothe sensing and control unit 195. However, in another exemplaryembodiment, the sensor 1420 can be coupled directly to the laser powersupply 130. Feedback from the sensor 1420 is used to control output fromlaser power supply 130/laser 120. That is, the energy density of thelaser beam 110 can be modified to ensure that the desired weld puddletemperature is achieved.

In yet a further exemplary embodiment of the invention, rather thandirecting the sensor 1420 at the puddle, it can be directed at an areaof the workpiece adjacent the weld puddle. Specifically, it may bedesirable to ensure that the heat input to the workpiece adjacent theweld is minimized. The sensor 1420 can be positioned to monitor thistemperature sensitive area such that a threshold temperature is notexceeded adjacent the weld. For example, the sensor 1420 can monitor theworkpiece temperature and reduce the energy density of the beam 110based on the sensed temperature. Such a configuration would ensure thatthe heat input adjacent the weld bead would not exceed a desiredthreshold. Such an embodiment can be utilized in precision weldingoperations where heat input into the workpiece is critical.

In another exemplary embodiment of the present invention, the sensingand control unit 195 can be coupled to a feed force detection unit (notshown) which is coupled to the wire feeding mechanism (not shown—but see150 in FIG. 1). The feed force detection units are known and detect thefeed force being applied to the wire 140 as it is being fed to theworkpiece 115. For example, such a detection unit can monitor the torquebeing applied by a wire feeding motor in the wire feeder 150. If thewire 140 passes through the molten weld puddle without fully melting itwill contact a solid portion of the workpiece and such contact willcause the feed force to increase as the motor is trying to maintain aset feed rate. This increase in force/torque can be detected and relayedto the control 195 which utilizes this information to adjust thevoltage, current and/or power to the wire 140 to ensure proper meltingof the wire 140 in the puddle.

It is noted that in some exemplary embodiments of the present invention,the wire is not constantly fed into the weld puddle, but can be done sointermittently based on a desired weld profile. Specifically, theversatility of various embodiments of the present invention allowseither an operator or the control unit 195 to start and stop feeding thewire 140 into the puddle as desired. For example, there are manydifferent types of complex weld profiles and geometry that may have someportions of the weld joint which require the use of a filler metal (thewire 140) and other portions of the same joint or on the same workpiecethat do not require the use of filler metal. As such, during a firstportion of a weld the control unit 195 can operate only the laser 120 tocause a laser weld of this first portion of the joint, but when thewelding operation reaches a second portion of the welding joint—whichrequires the use of a filler metal—the controller 195 causes the powersupply and 170 and the wire feeder 150 to begin depositing the wire 140into the weld puddle. Then, as the welding operation reaches the end ofthe second portion the deposition of the wire 140 can be stopped. Thisallows for the creation of continuous welds having a profile whichsignificantly varies from one portion to the next. Such capabilityallows a workpiece to be welded in a single welding operation as opposedto having many discrete welding operations. Of course, many variationscan be implemented. For example, a weld can have three or more distinctportions requiring a weld profile with varying shape, depth and fillerrequirements such that the use of the laser and the wire 140 can bedifferent in each weld portion. Furthermore, additional wires can beadded or removed as needed as well. That is, a first weld portion mayneed only a laser weld while a second portion only requires the use of asingle filler wire 140, and a final portion of the weld requires the useof two or more filler wires. The controller 195 can be made capable tocontrol the various system components to achieve such a varying weldprofile in a continuous welding operation, such that a continuous weldbead is created in a single weld pass.

FIG. 15 depicts a typical weld puddle P when welding in accordance withexemplary embodiments of the present invention. As described previouslythe laser beam 110 creates the puddle P in the surface of the workpieceW. The weld puddle has a length L which is a function of the energydensity, shape and movement of the beam 110. In an exemplary embodimentof the present invention, the beam 110 is directed to the puddle P at adistance Z from the trailing edge of the weld puddle. In suchembodiments, the high intensity energy source (e.g., the laser 120) doescause its energy to directly impinge on the filler wire 140 such thatthe energy source 120 does not melt the wire 140, rather the wire 140completes its melting because of its contact with the weld puddle. Thetrailing edge of the puddle P can be generally defined as the point atwhich the molten puddle ends and the weld bead WB created begins itssolidification. In an embodiment of the present invention the distance Zis 50% of the length L of the puddle P. In a further exemplaryembodiment, the distance Z is in the range of 40 to 75% the length L ofthe puddle P.

The filler wire 140 impacts the puddle P behind the beam 110—in thetravel direction of the weld—as shown in FIG. 15. As shown the wire 140impacts the puddle P as distance X before the trailing edge of thepuddle P. In an exemplary embodiment, the distance X is in the range of20 to 60% of the length of the puddle P. In another exemplaryembodiment, the distance X is in the range of 30 to 45% of the length Lof the puddle P. In other exemplary embodiments, the wire 140 and thebeam 110 intersect at the surface of or at a point above the puddle Psuch that at least some of the beam 110 impinges on the wire 140 duringthe welding process. In such an embodiment the laser beam 110 isutilized to aid in the melting of the wire 140 for deposition in thepuddle P. Using the beam 110 to aid in the melting of the wire 140 aidsin preventing the wire 140 from quenching the puddle P if the wire 140is too cool to be quickly consumed in the puddle P. However, as statedpreviously in some exemplary embodiments (as shown in FIG. 15) theenergy source 120 and beam 110 do not appreciably melt any portion ofthe filler wire 140 as the melting is completed by the heat of the weldpuddle.

In the embodiment shown in FIG. 15 the wire 140 trails the beam 110 andis in line with the beam 110. However, the present invention is notlimited to this configuration as the wire 140 can lead (in the traveldirection). Further, it is not necessary to have the wire 140 in linewith the beam in the travel direction, but the wire can impinge thepuddle from any direction so long as suitable wire melting occurs in thepuddle.

FIGS. 16A through 16F depict various puddles P with the footprint of thelaser beam 110 depicted. As shown, in some exemplary embodiments thepuddle P has a circular footprint. However, embodiments of the inventionare not limited to this configuration. For example, it is contemplatedthat the puddle can have elliptical or other shapes as well.

Further, in FIGS. 16A-16F the beam 110 is shown having a circularcross-section. Again, other embodiments of the present invention are notlimited in this regard as the beam 110 can have an elliptical,rectangular, or other shape so as to effectively create a weld puddle P.

In some embodiments, the laser beam 110 can remain stationary withrespect to the weld puddle P. That is, the beam 110 remains in arelatively consistent position with respect to the puddle P duringwelding. However, other embodiments are not limited in such a way, asexemplified in FIGS. 16A-16D. For example, FIG. 16A depicts anembodiment where the beam 110 is translated in a circular pattern aroundthe weld puddle P. In this figure the beam 110 translates such that atleast one point on the beam 110 overlaps the center C of the puddle atall times. In another embodiment, a circular pattern is used but thebeam 110 does not contact the center C. FIG. 16B depicts an embodimentwhere the beam is translated back-and-forth along a single line. Thisembodiment can be used to either elongate or widen the puddle Pdepending on the desired puddle P shape. FIG. 16C depicts an embodimentwhere the two different beam cross-sections are used. The first beamcross-section 110 has a first geometry and the second beam cross-section110′ has a second cross-section. Such an embodiment can be used toincrease penetration at a point in the puddle P while still maintaininga larger puddle size—if needed. This embodiment can be accomplished witha single laser 120 by changing the beam shape through the use of thelaser lenses and optics, or can be accomplished through the use ofmultiple lasers 120. FIG. 16D depicts a beam 110 being translated in anelliptical pattern in the puddle P. Again, such a pattern can be used toeither elongate or widen the weld puddle P as needed. Other beam 110translations can be utilized to create the puddle P.

FIGS. 16E and 16F depict a cross-section of a workpiece W and puddle Pusing different beam intensities. FIG. 16E depicts a shallow widerpuddle P which is created by a wider beam 110, while FIG. 16F depicts adeeper and narrow weld puddle P—typically referred to as a “keyhole”. Inthis embodiment, the beam is focused such that its focal point is nearthe upper surface of the workpiece W. With such a focus the beam 110 isable to penetrate through the full depth of the workpiece and aid increating a back bead BB on the bottom surface of the workpiece W. Thebeam intensity and shape are to be determined based on the desiredproperties of the weld puddle during welding.

The laser 120 can be moved, translated or operated via any known methodsand devices. Because the movement and optics of lasers are generallyknown, they will not be discussed in detail herein. FIG. 17 depicts asystem 1700 in accordance with an exemplary embodiment of the presentinvention, where the laser 120 can be moved and have its optics (such asits lenses) changed or adjusted during operation. This system 1700couples the sensing and control unit 195 to both a motor 1710 and anoptics drive unit 1720. The motor 1710 moves or translates the laser 120such that the position of the beam 110 relative to the weld puddle ismoved during welding. For example, the motor 1710 can translate the beam110 back and forth, move it in a circular pattern, etc. Similarly, theoptics drive unit 1720 receives instructions from the sensing andcontrol unit 195 to control the optics of the laser 120. For example,the optics drive unit 1720 can cause the focal point of the beam 110 tomove or change relative to the surface of the workpiece, thus changingthe penetration or depth of the weld puddle. Similarly, the optics driveunit 1720 can cause the optics of the laser 120 to change the shape ofthe beam 110. As such, during welding the sensing and control unit 195control the laser 120 and beam 110 to maintain and/or modify theproperties of the weld puddle during operation.

In each of FIGS. 1, 14 and 17 the laser power supply 130, hot wire powersupply 170 and sensing and control unit 195 are shown separately forclarity. However, in embodiments of the invention these components canbe made integral into a single welding system. Aspects of the presentinvention do not require the individually discussed components above tobe maintained as separately physical units or stand alone structures.

As described above, the high intensity energy source can be any numberof energy sources, including welding power sources. An exemplaryembodiment of this is shown in FIG. 20, which shows a system 2000similar to the system 100 shown in FIG. 1. Many of the components of thesystem 2000 are similar to the components in the system 100, and as suchtheir operation and utilization will not be discussed again in detail.However, in the system 2000 the laser system is replaced with an arcwelding system, such as a GMAW system. The GMAW system includes a powersupply 2130, a wire feeder 2150 and a torch 2120. A welding electrode2110 is delivered to a molten puddle via the wire feeder 2150 and thetorch 2120. The operation of a GMAW welding system of the type describedherein is well known and need not be described in detail herein. Itshould be noted that although a GMAW system is shown and discussedregarding depicted exemplary embodiments, exemplary embodiments of thepresent invention can also be used with GTAW, FCAW, MCAW, and SAWsystems, cladding systems, brazing systems, and combinations of thesesystems, etc., including those systems that use an arc to aid in thetransfer of a consumable to a molten puddle on a workpiece. Not shown inFIG. 20 is a shielding gas system or sub arc flux system which can beused in accordance with known methods.

Like the laser systems described above, the arc generation systems (thatcan be used as the high intensity energy source) are used to create themolten puddle to which the hot wire 140 is added using systems andembodiments as described in detail above. However, with the arcgeneration systems, as is known, an additional consumable 2110 is alsoadded to the puddle. This additional consumable adds to the alreadyincreased deposition performance provided by the hot wire processdescribed herein. This performance will be discussed in more detailbelow.

Further, as is generally known arc generation systems, such as GMAW usehigh levels of current to generate an arc between the advancingconsumable and the molten puddle on the workpiece. Similarly, GTAWsystems use high current levels to generate an arc between an electrodeand the workpiece, into which a consumable is added. As is generallyknown, many different current waveforms can be utilized for a GTAW orGMAW welding operation, such as constant current, pulse current, etc.However, during operation of the system 2000 the current generated bythe power supply 2130 can interfere with the current generated by thepower supply 170 which is used to heat the wire 140. Because the wire140 is proximate to the arc generated by the power supply 2130 (becausethey are each directed to the same molten puddle, similar to thatdescribed above) the respective currents can interfere with each other.Specifically, each of the currents generates a magnetic field and thosefields can interfere with each other and adversely affect theiroperation. For example, the magnetic fields generated by the hot wirecurrent can interfere with the stability of the arc generated by thepower supply 2130. That is, without proper control and synchronizationbetween the respective currents the competing magnetic fields candestabilize the arc and thus destabilize the process. Therefore,exemplary embodiments utilize current synchronization between the powersupplies 2130 and 170 to ensure stable operation, which will bediscussed further below.

FIG. 21 depicts a closer view of an exemplary welding operation of thepresent invention. As can be seen the torch 2120 (which can be anexemplary GMAW/MIG torch) delivers a consumable 2110 to a weld puddle WPthrough the use of an arc—as is generally known. Further, the hot wireconsumable 140 is delivered to the weld puddle WP in accordance with anyof the embodiments described above. It should be noted that although thetorch 2120 and tip 160 are shown separately in this figure, thesecomponents can be made integrally into a single torch unit whichdelivers both consumables 2110 and 140 to the puddle. Of course, to theextent an integral construction is utilized, electrical isolation withinthe torch must be used so as to prevent current transfer between theconsumables during the process. As stated above, magnetic fields inducedby the respective currents can interfere with each other and thusembodiments of the present invention synchronize the respectivecurrents. Synchronization can be achieved via various methods. Forexample, the sensing and current controller 195 can be used to controlthe operation of the power supplies 2130 and 170 to synchronize thecurrents. Alternatively a master-slave relationship can also be utilizedwhere one of the power supplies is used to control the output of theother. The control of the relative currents can be accomplished by anumber of methodologies including the use of state tables or algorithmsthat control the power supplies such that their output currents aresynchronized for a stable operation. This will be discussed relative toFIGS. 22A-C. For example, a dual-state based system and devices similarto that described in US Patent Publication No. 2010/0096373 can beutilized. US Patent Publication No. 2010/0096373, published on Apr. 22,2010, is incorporated herein by reference in its entirety.

Each of FIGS. 22A-C depicts exemplary current waveforms. FIG. 22Adepicts an exemplary welding waveform (either GMAW or GTAW) which usescurrent pulses 2202 to aid in the transfer of droplets from the wire2110 to the puddle. Of course, the waveform shown is exemplary andrepresentative and not intended to be limiting, for example the currentwaveforms can be that for pulsed spray transfer, pulse welding, surfacetension transfer welding, etc. The hot wire power supply 170 outputs acurrent waveform 2203 which also has a series of pulses 2204 to heat thewire 140, through resistance heating as generally described above. Thecurrent pulses 2204 are separated by a background level of a lessercurrent level. As generally described previously, the waveform 2203 isused to heat the wire 140 to at or near its melting temperature and usesthe pulses 2204 and background to heat the wire 140 through resistanceheating. As shown in FIG. 22A the pulses 2202 and 2204 from therespective current waveforms are synchronized such that they are inphase with each other. In this exemplary embodiment, the currentwaveforms are controlled such that the current pulses 2202/2204 have asimilar, or the same, frequency and are in phase with each other asshown. Surprisingly, it was discovered that having the waveforms inphase produces a stable and consistent operation, where the arc is notsignificantly interfered with by the heating current generated by thewaveform 2203.

FIG. 22B depicts waveforms from another exemplary embodiment of thepresent invention. In this embodiment, the heating current waveform 2205is controlled/synchronized such that the pulses 2206 are out-of-phasewith the pulses 2202 by a constant phase angle Θ. In such an embodiment,the phase angle is chosen to ensure stable operation of the process andto ensure that the arc is maintained in a stable condition. In exemplaryembodiments of the present invention, the phase angle Θ is in the rangeof 30 to 90 degrees. In other exemplary embodiments, the phase angle is0 degrees. Of course, other phase angles can be utilized so as to obtainstable operation, and can be in the range of 0 to 360 degrees, while inother exemplary embodiments the phase angle is in the range of 0 and 180degrees.

FIG. 22C depicts another exemplary embodiment of the present invention,where the hot wire current 2207 is synchronized with the weldingwaveform 2201 such that the hot wire pulses 2208 are out-of phase suchthat the phase angle θ is about 180 degrees with the welding pulses2202, and occurring only during the background portion 2210 of thewaveform 2201. In this embodiment the respective currents are notpeaking at the same time. That is, the pulses 2208 of the waveform 2207begin and end during the respective background portions 2210 of thewaveform 2201.

In some exemplary embodiments of the present invention, the pulse widthof the welding and hot-wire pulses is the same. However, in otherembodiments, the respective pulse-widths can be different. For example,when using a GMAW pulse waveform with a hot wire pulse waveform, theGMAW pulse width is in the range of 1.5 to 2.5 milliseconds and thehot-wire pulse width is in the range of 1.8 to 3 milliseconds, and thehot wire pulse width is larger than that of the GMAW pulse width.

It should be noted that although the heating current is shown as apulsed current, for some exemplary embodiments the heating current canbe constant power as described previously. The hot-wire current can alsobe a pulsed heating power, constant voltage, a sloped output and/or ajoules/time based output.

As explained herein, to the extent both currents are pulsed currentsthey are to be synchronized to ensure stable operation. There are manymethods that can be used to accomplish this, including the use ofsynchronization signals. For example, the controller 195 (which can beintegral to either or the power supplies 170/2130) can set asynchronization signal to start the pulsed arc peak and also set thedesired start time for the hot wire pulse peak. As explained above, insome embodiments, the pulses will be synchronized to start at the sametime, while in other embodiments the synchronization signal can set thestart of the pulse peak for the hot wire current at some duration afterthe arc pulse peak—the duration would be sufficient to obtained thedesired phase angle for the operation.

FIG. 23 represents another exemplary embodiment of the presentinvention. In this embodiment a GTAW welding/coating operation isutilized where a GTAW torch 2121 and an electrode 2122 create an arcinto which a consumable 2120 is delivered. Again the arc and the hotwire 140 are delivered to the same puddle WP to create a bead WB asshown. The operation of a GTAW embodiment is similar to that describedabove, in that the arc and the hot wire 140 are interacting with thesame weld puddle WP. Again, as with the above described GMAW operationthe current used to generate the arc in the GTAW operation issynchronized with the current for the hot wire operation. For example,the pulse relationship can be used as shown in FIGS. 22A to 22C.Further, the controller 195 can control the synchronization between thepower supplies using a dual-state table, or other similar methods ofcontrol. It should be noted that the consumable 2120 can be delivered tothe weld as a cold wire or can also be a hot-wire consumable. That is,both consumables 2110 and 140 can be heated as described herein.Alternatively, only one of the consumables 2120 and 140 can be thehot-wire as described herein.

In either of the GTAW or GMAW type embodiments discussed above(including the use of other arc type methods) the arc is positioned inthe lead—relative to the travel direction. This is shown in each ofFIGS. 21 and 23. This is because the arc is used to achieve the desiredpenetration in the workpiece(s). That is, the arc is used to create themolten puddle and achieve the desired penetration in the workpiece(s).Then, following behind the arc process is the hot wire process, which isdescribed in detail herein. The addition of the hot wire process addsmore consumable 140 to the puddle without the additional heat input ofanother welding arc, such as in a traditional tandem MIG process inwhich at least two arcs are used. Thus, embodiments of the presentinvention can achieve significant deposition rates at considerably lessheat input than known tandem welding methods.

As shown in FIG. 21, the hot wire 140 is inserted in the same weldpuddle WP as the arc, but trails behind the arc by a distance D. In someexemplary embodiments, this distance is in the range of 5 to 20 mm, andin other embodiments, this distance is in the range of 5 to 10 mm. Ofcourse, other distances can be used so long as the wire 140 is fed intothe same molten puddle as that created by the leading arc. However, thewires 2110 and 140 are to be deposited in the same molten puddle and thedistance D is to be such that there is minimal magnetic interferencewith the arc by the heating current used to heat the wire 140. Ingeneral, the size of the puddle—into which the arc and the wire arecollectively directed—will depend on the welding speed, arc parameters,total power to the wire 140, material type, etc., which will also befactors in determining a desired distance between wires 2110 and 140.

It should be noted that the operation of the hot wire current (e.g.,2203, 2203, or 2207) is similar to that described in detail herein whenan arc event is detected or predicted by either the controller 195 orthe power supply 170. That is, even though the current is pulsed thecurrent can be shut off or minimized as described herein if an arc iscreated or detected. Furthermore, in some exemplary embodiments, thebackground portions 2211 have a current level below an arc generationlevel for the wire 140 (which can be determined by the controller 195based on user input information), and rather than shutting the hot wirecurrent off when an arc is detected the power supply 170 can drop thecurrent to the background level 2211 for a duration or until it isdetermined that the arc is extinguished or will not occur (as generallydescribed previously). For example, the power supply 170 can skip apredetermined number of pulses 2203/2205/2207 or just not pulse for aduration, such as 10 to 100 ms, after which time the power supply 170can start the pulses again to heat the wire 140 to the appropriatetemperature.

As stated above, because at least two consumables 140/2110 are used inthe same puddle a very high deposition rate can be achieved, with a heatinput which is similar to that of a single arc operation. This providessignificant advantages over tandem MIG welding systems which have veryhigh heat input into the workpiece. For example, embodiments of thepresent invention can easily achieve at least 23 lb/hr deposition ratewith the heat input of a single arc. Other exemplary embodiments have adeposition rate of at least 35 lb/hr.

In exemplary embodiments of the present invention, each of the wires 140and 2110 are the same, in that they have the same composition, diameter,etc. However, in other exemplary embodiments the wires can be different.For example, the wires can have different diameters, wire feed speedsand composition as desired for the particular operation. In an exemplaryembodiment the wire feed speed for the lead wire 2110 is higher thanthat for the hot wire 140. For example, the lead wire 2110 can have awire feed speed of 450 ipm, while the trail wire 140 has a wire feedspeed of 400 ipm. Further, the wires can have different size andcompositions. In fact, because the hot wire 140 does not have to travelthrough an arc to be deposited into the puddle the hot wire 140 can havematerials/components which typically do not transfer well through anarc. For example, the wire 140 can have a tungsten carbide, or othersimilar hard facing material, which cannot be added to a typical weldingelectrode because of the arc. Additionally, the leading electrode 2110can have a composition which is rich in wetting agents, which can helpwetting the puddle to provide a desired bead shape. Further, the hotwire 140 can also contain slag elements which will aid in protecting thepuddle. Therefore, embodiments of the present invention allow for greatflexibility in the weld chemistry. It should be noted that because thewire 2110 is the lead wire, the arc welding operation, with the leadwire, provides the penetration for the weld joint, where the hot wireprovides additional fill for the joint.

In some exemplary embodiments of the present invention, the combinationof the arc and the hot-wire can be used to balance the heat input to theweld deposit, consistent with the requirements and limitations of thespecific operation to be performed. For example, the heat from the leadarc can be increased for joining applications where the heat from thearc aids in obtaining the penetration needed to join the work pieces andthe hot-wire is primarily used for fill of the joint. However, incladding or build-up processes, the hot-wire wire feed speed can beincreased to minimize dilution and increase build up.

Further, because different wire chemistries can be used a weld joint canbe created having different layers, which is traditionally achieved bytwo separate passes. The lead wire 2110 can have the required chemistryneeded for a traditional first pass, while the trail wire 140 can havethe chemistry needed for a traditional second pass. Further, in someembodiments at least one of the wires 140/2110 can be a cored wire. Forexample the hot wire 140 can be a cored wire having a powder core whichdeposits a desired material into the weld puddle.

FIG. 24 depicts another exemplary embodiment of current waveforms of thepresent invention. In this embodiment, the hot wire current 2403 is anAC current which is synchronized with the welding current 2401 (whetherit be GMAW or GTAW). In this embodiment, the positive pulses 2404 of theheating current are synchronized with the pulses 2402 of the current2401, while the negative pulses 2405 of the heating current 2403 aresynchronized with the background portions 2406 of the welding current.Of course, in other embodiments the synchronization can be opposite, inthat the positive pulses 2404 are synchronized with the background 2406and the negative pulses 2405 are synchronized with the pulses 2402. Inanother embodiment, there is a phase angle between the pulsed weldingcurrent and the hot wire current. By utilizing an AC waveform 2403 thealternating current (and thus alternating magnetic field) can be used toaid in stabilizing the arc. Of course, other embodiments can be utilizedwithout departing from the spirit or scope of the present invention. Forexample, in a system using a submerged arc welding (SAW) operation, theSAW current waveform can be an AC waveform and the hot wire currentwaveform is an AC or a pulsed DC power waveform, where each of thewaveforms are synchronized with each other.

It is also noted that embodiments of the present invention can be usedwhere the welding current is a constant or near constant currentwaveform. In such embodiments, an alternating heating current 2403 canbe used to maintain the stability of the arc. The stability is achievedby the constantly changed magnetic field from the heating current 2403.

FIG. 25 depicts another exemplary embodiment of the present invention,where the hot wire 140 is positioned between two tandem arc weldingoperations. In FIG. 25 the arc welding operations are depicted as GMAWtype welding, but can also be GTAW, FCAW, MCAW or SAW type systems. Inthe figures, the lead torch 2120 is coupled to a first power supply 2130and delivers a first electrode 2110 to the puddle via an arc weldingoperation. Trailing the lead arc is the hot wire 140 (which is depositedas discussed above). Trailing the hot wire 140 is a trailing arc weldingoperation using a second power supply 2130′, a second torch 2120′ and asecond arc welding wire 2110′. Thus, the configuration is similar tothat of a tandem GMAW welding system but has a hot-wire 140 depositedinto the common puddle between the torches 2120 and 2120′. Such anembodiment further increases the deposition rate of materials into thepuddle. It should be noted that embodiments of the present invention canuse additional welding torches and/or hot wire consumables in a singleoperation, and are not limited to the embodiments shown in the Figures.For example, more than hot-wire can be used to deposit additionalmaterials into the puddle during a single pass. As mentioned above, SAWprocesses can be used rather than the GMAW processes generally discussedherein. For example, the embodiment shown in FIG. 25 can utilize leadingand trailing SAW processes with a similar configuration as to that shownin this figure. Of course, rather than a shielding gas, a granular fluxwould be used to shield the arcs. The overall method or operation andcontrol, as discussed above, are similarly applicable when using otherwelding methodologies, such as SAW. For example, FIG. 25A depictsexemplary waveforms that can be used in an SAW system with a hot-wire asdescribed herein. As depicted, the lead SAW current waveform 2501 is anAC waveform having a plurality of positive pulses 2503 and a pluralityof negative pulses 2505, while the trailing SAW current 2521 is also anAC waveform having a plurality of positive pulses 2523 and a pluralityof negative pulses 2525, where the trailing waveform 2521 isout-of-phase from the leading waveform 2501 by a phase angle α. Inexemplary embodiments of the present invention, the phase angle α is inthe range of 90 to 270 degrees. It is also noted that in the embodimentshown the +/− offset between the waveforms 2501 and 2521 is different inthat the trailing waveform 2521 has a larger negative offset than theleading waveform 2501. In other exemplary embodiments, the offset can bethe same, or can be reversed. The hot wire current 2510 shown in a pulsecurrent having a plurality of positive pulses 2511 separated by abackground level 2513 where the waveform 2510 has an offset phase angle8, which is different than the phase angle α. In an exemplaryembodiment, the hot wire phase angle 8 is in the range of 45 to 315degrees, but is different than the phase angle α.

It is noted that although the above discussion was directed to a SAWtype operation, other exemplary embodiments using a similarsynchronization methodology can be of a GMAW, FCAW, MCAW, or GTAW typeoperation, or a combination thereof.

As stated above, embodiments of the present invention can greatlyincrease the deposition of materials into the puddle while keeping thetotal heat input lower than traditional tandem systems. However, someexemplary embodiments can create a weld bead WB shape which is higherthan traditional tandem methods. That is, the weld bead WB tends tostand up higher above the surface of the workpiece and does not wet outto the sides of the weld bead WB as much as tandem systems. Generally,this is because the hot wire 140 will aid in quenching the puddlefollowing the leading arc welding operation. Therefore, some exemplaryembodiments of the present invention utilize systems and components toaid in widening or wetting out the puddle during a welding/coatingoperation.

FIG. 26 depicts an exemplary embodiment, where two GMAW torches 2120 and2120′ are not positioned in line, but are rather positioned in aside-by-side position—as shown, where the hot wire 140 is trailingbehind the two torches 2120/2120′. In this embodiment, having the twoGMAW arcs in a side-by-side configuration will widen the puddle WP andaid in wetting out the puddle to flatten the weld bead WB. As with theother embodiments, the hot wire 140 trails the arc welding operation andcan be positioned on the center-line of the weld bead WB behind the arcwelding operations. However, its is not necessary that the hot wire 140remain in the centerline as the hot wire can be oscillated or movedrelative to the puddle during the welding operation.

FIG. 27 depicts another exemplary embodiment where lasers 2720 and 2720′are used on either side of the weld puddle WP to help flatten out thepuddle or aid in the wetting of the puddle. The lasers 2720/2720′ eachemit beams 2710/2710′, respectively, on the sides of the puddle to addheat to the puddle and aid in wetting the puddle so that the puddleshape is desirable. The lasers 2720/2720′ can be of the type describedherein and can be controlled as described above. That is, the lasers canbe controlled by the controller 195, or a similar device, to provide thedesired weld bead shape. Furthermore, rather than using two lasers toachieve the desired weld bead shape a single laser can be used with abeam splitter which splits the beam 2710 and directs the split beams tothe appropriate position on the weld puddle to achieve the desired weldbead shape. It is noted that the leading arc welding process is notdepicted in FIG. 27 for purposes of clarity.

In a further exemplary embodiment, a single laser beam 2710 can be usedthat is directed to the puddle just downstream of the arc process ordownstream of the hot wire 140 (in the travel direction) where the beam2710 is oscillated from side to side to aid in flattening the puddle. Insuch embodiments a single laser 2720 can be used and directed to areasof the puddle where it is desired to aid in wetting out the puddleduring welding. The control and operation of the laser 2720 is similarto the control and operation of the laser 120 described above inrelation to FIG. 1, etc.

FIG. 28 depicts another exemplary embodiment of the present invention.In this exemplary embodiment, a GTAW (or GMAW, FCAW, MCAW) electrode2801 is utilized for the arc welding process and a magnetic probe 2803is positioned adjacent to the electrode 2801 to control the movement ofthe arc during welding. The probe 2803 receives a current from themagnetic control and power supply 2805, which may or may not be coupledto the controller 195, and the current causes a magnetic field MF to begenerated by the probe 2803. The magnetic field interacts with themagnetic field generated by the arc and can thus be used to move the arcduring welding. That is, the arc can be moved from side to side duringwelding. This side to side movement is used to widen the puddle and aidin wetting out the puddle to achieve the desired weld bead shape.Although not shown for clarity, following the arc is a hot-wireconsumable as discussed herein to provide additional filling for theweld bead. The use and implementation of a magnetic steering system isgenerally known by those in the welding industry and need not bedescribed in detail herein.

It is, of course, understood that the embodiments in either of FIGS. 26and 28 (as well as the other shown embodiments described herein) can usethe laser 2720 to aid in the shape of the weld puddle as describedherein.

FIG. 29 depicts another exemplary current waveform that can be used withexemplary embodiments of the present invention as described herein. Asexplained previously, when welding coated materials (e.g., galvanizedmaterials) with traditional welding methods issues can arise due toporosity and spatter. Further, as additionally explained hereinembodiments of the present invention can address the issues of porosityand spatter and achieve significantly improved performance overtraditional welding and overlaying systems. For example, a method andsystem of using both arc welding and hot-wire can provide improvedperformance, as discussed herein relative to FIGS. 20 to 28 herein. FIG.29 represents a further exemplary embodiment of a current waveform thatcan be used for the arc welding operation generally depicted in FIG. 20.That is, the current waveform in FIG. 29 can be generated by the powersupply 2130 and provided to the electrode 2110. The current waveform inFIG. 29 will now be discussed.

As shown in FIG. 29, the exemplary current waveform 3000 is an AC typewaveform having both positive and negative portions. When usingexemplary embodiments of the present invention, use of the waveform 3000can provide the porosity and spatter performance discussed previously athigh travel speeds and deposition rates. In fact, the advantages of thewaveform 3000 can be achieved with or without the use of a hot-wire 140in the same weld puddle—this will be discussed in more detail below. Thewaveform 3000 shown in FIG. 29 is intended to be exemplary andembodiments of the present invention are not limited thereto.

As shown, the waveform 3000 has a number of phases. Specifically, thewaveform 3000 has at least a droplet transfer phase P1 and droplet buildphase P2. The droplet transfer phase P1 contains at least one droplettransfer pulse 3010 which is used to transfer the droplet D from theelectrode 2110 to the workpiece 115. Typically, the droplet transferpulse 3010 is a positive current pulse and has a profile which allowsfor the smooth transfer of the droplet D to the workpiece, for examplewith limited spatter. In the embodiment shown, the pulse 3010 has anexponential current ramp rate 3011 to a peak current level 3013. Inexemplary embodiments, the peak current level 3013 is in the range of300 to 500 amps. Of course, other peak current levels 3013 can be usedwithout departing from the spirit or scope of the present invention.Further, the pulse 3010 can have a current ramp down profile 3015 whichallows for the electrode 2110 to neck down between the droplet D and theelectrode 2110 so that when the droplet D breaks off the spatter islimited. Further, although an exponential slope 3011 is shown, otherembodiments are not limited to this profile. Other current ramp rateprofiles can be used without departing from the scope of the presentinvention so long as the current ramp rate allows for the smoothtransition of the droplet D to the workpiece 115. That is, in someexemplary embodiments, known droplet transfer pulse profiles can beused. At the end of the droplet transfer pulse 3010 the droplet D makescontact with the puddle on the workpiece 115 and is transferred to theworkpiece 115. In exemplary embodiments of the present invention, at theend of the droplet transfer pulse 3010 the electrode 2110 is in ashorted condition, in that the droplet D is contacting both the puddleand the electrode 2110. In such exemplary embodiments, a short clearingportion 3020 is present in the waveform 3000. The short clearing portion3020 can be any known short clearing function which is capable ofclearing a short condition with minimal or no spatter. For example, theshort clearing function can be similar to that used in the known STT(surface tension transfer) technology. In the embodiment shown, duringthe short clearing portion 3020, the current is dropped to a level 3021which is less than the background level 3025 until the droplet D breaksaway from the electrode 2110. Following the break, the current isincreased to a plasma boost level 3023 to allow for burn back of theelectrode 2110 away from the puddle, after which the current returns tothe background level 3025 before the droplet build phase P2 begins. Itis noted that in some exemplary embodiments, a short circuit transfermethod may not be used to transfer the droplet, and as such no shortclearing portion 3020 need be present in the waveform 3000. Of course,even in such embodiments it is likely that shorting events may stilloccur. Therefore, in such embodiments, the power supply 2130 uses ashort clearing function to clear the short. Accordingly, in someexemplary embodiments there is no intentional short condition created atthe conclusion of the droplet transfer pulse 3010, but if it does occura short clearing function is initiated and can be similar to the portion3020 shown in FIG. 29.

After the droplet transfer phase P1, and any short clearing portion 3020(if present), the droplet build phase P2 begins. As shown in FIG. 29 thedroplet build phase P2 begins after the short clearing portion 3020 andafter the current returns to the background level 3025. However, inother exemplary embodiments, the droplet build phase P2 can begindirectly after the short clear portion 3020 such that the current doesnot return to and remain at the background current level 3025. Forexample, the current can drop from the plasma boost 3023 directly intothe droplet build phase P2. The droplet D, which is to be transferred,is primarily formed during the droplet build phase P2. As shown, thedroplet build phase P2 utilizes an AC waveform profile to create thedroplet D. This AC waveform profile is used to create a droplet of thedesired size and stability, while at the same time minimizing heatinput. During the droplet build phase P2, as shown, there is nointentional transfer of a droplet D during this phase of the waveform.Instead, this portion of the waveform is used to construct the droplet Dfor transfer in the transfer phase P1. Of course, it is recognized thatin the reality of welding there can be inadvertent droplet transfer orshort circuit from time to time. However, there is no intentionaldroplet transfer during the build phase P2.

As shown, at the beginning of the droplet build phase P2, the currententers a first negative polarity droplet build pulse 3030. That is, thecurrent changes from a positive polarity to a negative polarity at anegative background level 3031 and is maintained at that level for aperiod of time T1. In exemplary embodiments, the current level 3031 isin the range of 30 to 300 amps. In other exemplary embodiments, thecurrent level 3031 is in the range of 35 to 125 amps. Further, inexemplary embodiments, the time T1 is in the range of 400 μs to 3 ms. Infurther exemplary embodiments, the time T1 is in the range of 700 μs to2 ms. This can be referred to as a negative polarity pulse. As shown,during this build pulse 3030, a new droplet D begins to form at the endof the electrode 2110, and because the current is negative the heatinput is relatively low (compared to a positive current flow). However,as is generally understood, during a negative current flow the cathodespot can tend to move up the electrode 2110, which tends to cause thedroplet D to turn upward and destabilize. Thus, after the first dropletbuild pulse 3030 a first droplet stabilizing pulse 3040 is used, wherethe first droplet stabilizing pulse 3040 has a positive peak currentlevel 3041. This peak level 3041 is maintained for a time T3, and inexemplary embodiments can be in the range of 300 to 500 amps. In otherexemplary embodiments, the current 3041 is in the range of 350 to 400amps. In exemplary embodiments, the time T3 is in the range of 300 μs to2.5 ms. In further exemplary embodiments, the time T3 is in the range of500 μs to 1.5 ms. As shown, in addition to continuing to build thedroplet D the stabilizing pulse 3040 returns the droplet D to a morestable position directed towards the workpiece 115. This allows thedroplet to grow in a more stable fashion. In the exemplary embodimentshown the current level 3041 of the stabilizing pulse 3040 is higher (inmagnitude) than the current level 3031 of the pulse 3030, and is shorterin duration (i.e., T3 is shorter than T1). In exemplary embodiments, thecurrent level 3041 is in the range of 1.5 to 3 times the magnitude ofthe negative current level 3031. Further, in exemplary embodiments, theduration T1 is 1.25 to 3 times the duration T3 of the positive peakcurrent 3041.

However, in other exemplary embodiments, the positive peak current level3041 could be less (in magnitude), and/or longer in duration than thenegative peak current 3031. For example, in some exemplary embodiments,the stabilizing peak level 3041 is in the range of 50 to 125 amps lower(in magnitude) than the peak level 3031 of the droplet build pulse 3030.This can be affected by the type of electrode E being used, and therelative durations and peak levels of the pulses 3030/3040 should beselected to provide the desired droplet build and stabilitycharacteristics.

As shown, after the first droplet stabilizing pulse 3040 a seconddroplet build pulse 3030′ and stabilization pulse 3041′ is used. In theembodiment shown, each of the second droplet build pulse 3030′ andstabilization pulse 3041′ have the same current levels 3031/3041 anddurations T1/T3 as the first pulse 3030/3040. However, in otherexemplary embodiments, either, or both, of the durations of and the peakcurrent levels 3031′/3041′ can be less than that of the first pulses3030/3040. That is, the first build and stabilization pulses can be usedto provide the largest amount of droplet building energy, while thefollowing pulse(s) provide less droplet build energy. Further, in otherembodiments, either, or both, of the durations of and the peak currentlevels 3031′/3041′ can be greater than that of the first pulses3030/3040. In such embodiments, the droplet build energy can increasewith subsequent pulses.

As shown in FIG. 29, following the second stabilization pulse 3040′ is athird droplet build pulse 3030″. This pulse 3030″ either completes theformation of the droplet D or brings the droplet D to near completion inits formation and is followed by another droplet transfer pulse 3010 todeposit the droplet D on the work piece. In the embodiment shown, thepulse 3030″ has a current level 3031″ which is the same as the currentlevels 3031/3031′ of the previous pulses 3030/3030′. However, in otherexemplary embodiments, the current level 3031″ can be higher or lowerthan that of the previous pulses depending on the desired energy input.Also, in the embodiment shown, the current returns to the backgroundlevel 3025 for a brief moment before the droplet transfer pulse 3010begins. However, in other exemplary embodiments, the current can proceeddirectly into the droplet transfer pulse 3010. Also, as shown, the finaldroplet build pulse 3030″ has a peak current level 3031″ for a durationT2 which is less than the duration (e.g., T1) than the previous pulses3030/3030′. This is to ensure that the droplet reaches the proper sizeand does not destabilize prior to transferring the droplet D. However,in other exemplary embodiments, the duration T2 can be the same as, orlonger than, the duration T1 of previous pulses 3030/3030′. This candepend on the desired droplet size prior to transfer.

It should be noted that the waveform 3000 depicted in FIG. 29 isintended to be exemplary, and other similarly functioning waveforms canbe used without departing from the spirit or scope of the presentinvention. For example, unlike the embodiment shown in FIG. 29, thetransition to the droplet transfer phase P1 can come from a dropletstabilizing pulse, instead of a droplet build pulse, as shown. Further,in other exemplary embodiments, the droplet build phase P2 cantransition to a droplet stabilization and advancement stage, where thecurrent is changed to a positive current level (after either of thepulses 3030/3040) which is lower than the peak level 3040′ (for example,lower by more than 50%). This will aid in stabilizing the droplet andslow the build of the droplet such that the droplet can be pushed closerto the puddle by the wire feeding, prior to the transition phase P1. Infurther exemplary embodiments, the droplet can be cause to make contactwith the puddle and transferred via the short circuit (for example,using surface tension transfer—STT). In other exemplary embodiments, thedroplet can be advanced to the puddle (after the build phase P2) via thewire feeder to make contact with the puddle, and then the current iscontrolled such that the electrode is necked down and the wire isreversed from the puddle, leaving the droplet in the puddle. In furtherexemplary embodiments, the low current positive pulse (the stabilizingpulse discussed above) can be an intermediate pulse/phase between thebuild phase P2 and the transition phase P1. That is, from the buildphase P2, the current will enter a low positive current pulsestabilization phase, and then to the pulse transfer phase P1. In thepulse stabilization phase, the current pulse is to have a current peakand duration to stabilize the droplet and prepare the droplet fortransfer. In exemplary embodiments, the positive stabilization pulse inthis stabilization phase, has a peak current which is in the range of 35to 60% of the peak current level 3041′ immediately preceding thisstabilization phase. The duration of this stabilization peak current canbe fixed (by a controller) or can be variable. For example, a controllercan monitor the amount of energy created during the droplet build phaseP2 and then adjust the peak and/or duration of the positivestabilization pulse to ensure that a proper amount of energy isgenerated before the droplet transfer phase P1. That is, a systemcontroller (e.g., 195) can determine an desired energy input X (e.g., injoules) that is to be achieved prior to droplet transfer, and if theamount of energy input during the phase P2 is below X, the controller195 can use the positive current stabilization phase (between phases P1and P2) to add the determined additional energy. In further exemplaryembodiments, it may be desirable or necessary to transfer the droplet Dprior to the transfer phase P1, and thus the current pulse in the abovedescribed stabilization phase can be used to transfer the droplet. Forexample, during the build phase the droplet D may build faster thandesired or anticipated such that at or near the end of the build phaseP2 the droplet is ready to be transferred, or about to make contact withthe puddle. This can be detected by the controller 195 by monitoring thecurrent, voltage, power and/or dv/dt of the welding signal. If this isdetected, the controller can use an either a pulse 3040, or a smallerpositive pulse (like that discussed above during the stabilizationphase) to transfer the droplet D—prior to initiating the pulse 3010.Once the transfer is complete, the controller 195 causes the transferpulse 3010 to be skipped and then begins the build phase P2 for the nextdroplet.

It should be noted that while the waveform 3000 in FIG. 29 is shown withthree build pulses 3030/3030′/3030″ and two stabilization pulses3040/3040′, other exemplary embodiments are not limited in this way.That is, in some embodiments, there can be more pulses 3030/3040, orless pulses. In fact, in some exemplary embodiments, there can be only asingle droplet build pulse 3030 and droplet stabilization pulse 3040. Ofcourse, the number of pulses should be used to achieve the desireddroplet size and stability to ensure appropriate transfer.

In exemplary embodiments of the present invention, the droplet transferpulses 3010 has a cycle duration in the range of 2 to 50 ms. In someexemplary embodiments, subsequent droplet transfer pulses 3010 have afrequency in the range of 20 to 300 Hz, and the droplet build andstabilization pulses have a frequency in the range of 300 to 1000 Hz. Ofcourse, other frequencies can be used to achieve the desiredperformance. However, in exemplary embodiments of the present invention,to the extent that there are multiple combinations of build andstabilization pulses (as in FIG. 29) the frequency of these pulses willbe higher than that of the transfer pulses 3010. In exemplaryembodiments, the frequency of the build/stabilization pulses will be inthe range of 1.5 to 3 times that of the transfer pulses 3010.

As previously discussed with respect to other embodiments, the waveform3000 is generated by the power supply 2130, the output of which can becontrolled by either the power supply 2130 or the controller 195, orboth. With respect to the length of the droplet build phase P2, theduration TDF is controlled by the controller 195 and/or the power supply2130. For example, in some exemplary embodiments a timer is used ineither the controller 195 or the power supply 2130 and the duration TDFis predetermined prior to the welding operation beginning. Duringoperation, the length of the droplet build phase P2 is controlled tocoincide with the predetermined duration TDF, such that at theconclusion of the duration TDF a following transfer pulse 3010 isinitiated. The duration TDF can be determined via algorithms, look uptables, etc. based on user input information related to the weldingoperation. Further, in exemplary embodiments, the frequency and/orduration of the pulses in the droplet build phase P2 is determined(e.g., by the controller 195) so that the droplet build phase P2 ends ata point which is desirable for transition to the droplet transferportion P1. For example, as shown in FIG. 29, the droplet build phase P2is ended at the end of a droplet build pulse 3031″. In further exemplaryembodiments, the controller 195 (or power supply 2130) uses a countertype circuit to count the number of pulses during the droplet buildphase P2 such that the duration TDF is of a duration that allows thedetermined number of pulses N to occur. Stated differently, thecontroller 195 determines a number N of pulses that are to be usedduring the droplet build phase P2 and the frequency of the pulses, andcontrols the operation of the system such that the duration TDF allowsthe determined number N of pulses to be implemented before the followingdroplet transfer phase P1. In other exemplary embodiments, thecontroller 195 can control the duration TDF of the build phase P2 basedon the output energy into the welding operation. That is, the controller195 can determine a desired amount of energy to be input to the processduring the build phase P2, and controls the waveform output to ensurethat the predetermined amount of energy is output during the phase P2with the pulses, and then trigger the following transfer pulse 3010 whenthe predetermined amount of energy (e.g., joules) has been reached forthe given phase P2. In other exemplary embodiments, other controlmethodologies can be used to ensure a desired droplet size and stabilityis achieved before transfer.

In exemplary embodiments of the present invention, the duration of thebuild phase TDF is in the range of 1.5 to 5 times longer than theduration of the transfer phase P1.

As acknowledged above, during some welding operations it is possiblethat a short circuit condition can exist during the droplet build phaseP2, which may result in the transfer of a droplet prematurely (duringthe build phase P2). In such a situation embodiments of the presentinvention will initiate a short clearing function to break the shortcondition, and restart the droplet build phase P2 to ensure a properdroplet is formed before transfer.

FIG. 30 depicts another exemplary waveform/welding process that can beused with embodiments of the present invention to weld coated materials.Like the waveform shown in FIG. 29, the embodiment in FIG. 30 can beused with or without an additional hot-wire consumable as describedherein, and can provide the desired porosity and spatter performance, asdiscussed further herein. Like FIG. 29, the waveforms shown in FIG. 30are intended to be exemplary. It should be noted that in the followingdiscussion the voltage 3200 and current 3100 waveforms will be generallydiscussed together as the phases of the droplet build and transfer arediscussed, and will only be discussed separately as needed. The portionsof the respective waveforms 3100/3200 that correspond with each otherwill have similar numbers (e.g., 3101 and 3201, etc.) so as to allow foreasy correlation.

FIG. 30 depicts both a current waveform 3100 and a voltage waveform 3200for an exemplary embodiment of the present invention, as well asdepicted the phases of the transfer of the droplet D from the consumable2110. Like the waveform 3000 in FIG. 29, the waveforms in FIG. 30 arealso AC waveforms. Like the waveform 3000, the waveform 3100 aids incontrolling the interaction of any coating (such as zinc) of a workpieceduring a welding operation. As shown, the waveform 3100 begins anegative low current level 3101/3201. This current level can be in therange of 15 to 100 amps and can be based on the wire feed speed beingused for the operation. In exemplary embodiments, the current level isselected to keep the temperature below the vaporization temperature ofthe workpiece coating—for example zinc. This is aided because thecurrent is in a negative polarity state. Specifically, by having thecathode spot on the electrode 2110 instead of the workpiece, the anodespot is stationary (on the workpiece) and the temperature can be keptlow enough so that a coating is not vaporized. At point A the current isincreased during a controlled ramp phase 3103/3203 to cause the tip ofthe electrode 2110 to melt quicker and create the droplet D. However,the current is increased at a controlled rate so as to ensure that thecathode spot of the arc climbs the electrode 2110 in a controlledmanner. If the ramp rate is too high the cathode spot can becomeunstable. In exemplary embodiments the current ramp rate during thecontrolled ramp phase 3103 is in the range of 25 to 100 amps/ms. Duringthis phase the cathode spot moves in a controlled manner, thus keepingthe current density of the arc controlled. In exemplary embodiments, theramp rate can be determined by a controller of the power supply basedupon user input information, such as wire feed speed and electrode type(which can include, electrode material, diameter, etc., either incombination or separately), etc.

Once the arc envelopes the droplet D (at point B) then current can beramped up more quickly to a negative peak current level 3105/3205. Thetransition from the controlled ramp rate portion 3103 to a highercurrent ramp rate (at point B) can be determined in different ways. Inexemplary embodiments, the power supply can maintain the controlled ramprate for a predetermined period of time, which would be set by thecontrolled based on user input data such as WFS, electrode information,etc. Thus, at the expiration of the duration the current ramp rate ischanged from the ramp rate during the phase 3103 to a higher ramp rate(which could be the fastest capable ramp rate of the power supply). Inother exemplary embodiments, the power supply can use a predeterminedvoltage level, such that when this voltage level is reached the powersupply changes from the ramp rate during phase 3103 to a higher ramprate. Again, this predetermined voltage threshold is determined by thepower supply based on user input data, such as WFS, electrode type, etc.In exemplary embodiments, the voltage threshold is determined to be avoltage level at which it is understood that the arc is fully envelopingthe formed droplet D on the 2110 electrode—that is, at least some of thearc is contacting the electrode 2110 above the droplet D. The peakcurrent level 3105 is a current level which provides the desired dropletsize, and in exemplary embodiments can be in the range of 150 to 400amps. In exemplary embodiments, the peak current level 3105 can bedetermined by the controller of the power supply based upon user inputinformation, such as wire feed speed and electrode type, etc.

It is noted that during the first three phases of the waveform 3100, thecurrent is kept negative so that the anode spot (on the workpiece) isrelatively stable and focused in the puddle on the workpiece. Because ofthis, the arc does not tend to vaporize any new coating (e.g., zinc)which is outside of the puddle, for example in the heat affected zone.Thus, no (or limited amounts) of newly vaporized coating is created tominimize the absorption of that vaporized material into the puddle.

During the negative peak current phase 3105 the cathode spot of the arccontinues to climb above the droplet D. However, if the cathode spotclimbs too high above the droplet D the arc can become unstable. Toprevent this from occurring, at point C the current is rapidly changedfrom negative to positive until it reaches a first positive currentlevel 3107. Like the duration of the ramp portion 3103, the duration ofthe negative peak portion 3105 can be determined by either apredetermined time duration, or a predetermined voltage threshold, whichare set based on user input information. In either case, the duration ofthe peak 3105 should be selected such that the cathode spot does notclimb appreciably higher than the droplet D on the electrode 2110. Ifthe spot gets too high, the arc will become unstable and will begin tovaporize any coating near the puddle edge. By switching to a sufficientpositive current level 3107, the current density of the arc is keptfocused within the puddle. That is, with a positive current the currentdensity now goes through the electrode 2110 and causes the electrode2110 to begin to neck down, thus maximizing the arc pinch force. Thetransition from the negative peak 3105 to the first positive currentlevel should occur quickly to ensure that the cathode spot (now moved tothe workpiece) remains in the puddle. In exemplary embodiments of thepresent invention, the first positive current level 3107 is a currentlevel in the range of 50 to 200 amps, and in some embodiments is in therange of 75 to 150 amps. The first current level can be predetermined bythe power supply controller based on user input information related tothe welding process, such as WFS and electrode type (including materialand/or diameter, etc).

Once the current reaches the first positive current level 3107, thecurrent then enters a positive current ramp phase 3109 in which thecurrent is ramped to a positive peak current level 3111. Again, like thenegative ramp phase 3103, the positive ramp phase is also controlled inexemplary embodiments to provide controlled increase of the arc andcontrolled melting of the electrode 2110. As with other exemplaryembodiments described herein, the electrode 2110 can be either a solidor cored electrode type. When using a cored electrode type (whethersolid or flux cored) a controlled current ramp rate (in both sections3103 and 3109) aids in preventing the elements in the core fromoverheating, which can compromise the weld quality. In exemplaryembodiments of the present invention the ramp rate of the positivecontrolled portion 3109 is faster than the ramp rate of the negativeportion 3103, and can be in the range of 300 to 600 amps/ms. In furtherexemplary embodiments, the ramp rate is in the range of 400 to 500amps/ms. The ramp rate can be selected based on input data regarding thewelding operation, including WFS and electrode. When the current reachesthe peak level 3111 its increase is stopped. The peak level 3111 is acurrent level is a current level which ensures that the droplet D willreach a size sufficient for transfer to the puddle, and create asufficient pinch force to allow for droplet separation. In exemplaryembodiments, the peak current level 3111 has a peak level which ishigher than the peak level 3105. In exemplary embodiments, the peakcurrent level 3111 is in the range of 300 to 600 amps, and is selectedbased on user input welding data, such as WFS, electrode information,etc. During this phase of the waveform, the electrode 2110 neckssignificantly and the waveform the droplet D begins to separate from theelectrode 2110. The peak current 3111 is maintained at the peak levelfor a duration until point D, as shown in FIG. 30. In exemplaryembodiments, the duration of the peak current 3111 is maintained untilthe droplet tether (or neck) is sufficiently small that transfer of thedroplet D will likely occur. This duration can be determined using apredetermined time duration (based on user input information) or bymonitoring dv/dt of the arc and when the voltage rate of change reachesa predetermined threshold it is determined that the droplet issufficiently formed and that the current can begin ramping down from thepeak. In each of the embodiments, either the time duration or thevoltage change rate (dv/dt) can be set by the power supply controllerbased upon user input information, including WFS, electrode, etc. Asshown, once the predetermined threshold (whether duration or dv/dt) isreached, at point D, the current enters a controlled ramp down phase3112 until the current reaches a polarity switching current level 3113.It is noted that in each embodiment, the predetermined duration orpredetermined dv/dt level is set at a threshold such that the transferof the droplet D is likely to occur. In exemplary embodiments, thisthreshold is set such that the tether T of the droplet D to theelectrode 2110 is no more than 75% the diameter of the electrode 2110.In other exemplary embodiments, the tether T of the droplet is no morethan 50% the diameter of the electrode 2110.

During the ramp down 3112 of the current the ramp down rate iscontrolled such that the arc remains stable and the cathode spot on thepuddle does not move significantly relative to the puddle. In someexemplary embodiments, this ramp down rate is the same as the ramp uprate of the phase 3109. However, in other exemplary embodiments the rampdown rate can be either slower or faster. The ramp down rate can bedetermined based on user input data, including WFS, electrode type, etc.In exemplary embodiments, the ramp down rate is in the range of 300 to1000 amps/ms. In other exemplary embodiments, the ramp down rate is inthe range of 400 to 750 amps/ms.

As shown, the current is ramped down to a polarity switching currentlevel 3113, which can be in the range of 100 to 200 amps, and in otherembodiments can be in the range of 75 to 150 amps. In some exemplaryembodiments, the polarity switching current level 3113 is the samecurrent level as the point 3107, while in other embodiments it can bedifferent. In exemplary embodiments, the current level 3113 is apredetermined current level set point based on user inputs regarding theprocess, such as WFS, electrode type, etc. Once this current level isreached the current is switched, as quickly as possible to a negativepolarity tail out level 3115. This switch is to be made quickly becauseif the current level stays too low for too long the cathode spot on thepuddle will begin to wander and can approach the edge of the puddle.This will cause additional coating to be vaporized, which isundesirable. By switching quickly to a negative polarity the cathodespot is moved back to the electrode 2110 as the droplet D nears theseparation point from the electrode 2110. However, at this time thecurrent is still going through the droplet D and not around the dropletD. This allows for a stable transfer of the droplet D. In exemplaryembodiments, the negative polarity tail out level 3115 has a currentwhich is higher (in magnitude) than the negative low current level 3101(which can also be called a background level). The current is thenramped down to aid in the droplet D transferring without a spatterevent. In the embodiment shown in FIG. 30, the droplet D is transferredvia a short circuit transfer where the droplet D is in contact with thepuddle while still being connected to the electrode 2110. This method oftransfer can provide a very fast transfer method. However, in otherexemplary embodiments the droplet D can be transferred via “free flight”transfer where no short (physical connection) is created. It is notedthat the use of a short circuit transfer methodology utilizes theshortest arc length, and at point 3117 the current can be reduced orshut off so as to prevent a spatter event from occurring as the dropletbreaks off. In exemplary embodiments of the present invention using ashort circuit transfer method, the surface tension of the puddle shouldbe sufficient to pull the droplet D from the electrode 2110. In suchembodiments, the current need only be reduced to a low level or thebackground level (3101) and need not be shut off. However, in otherexemplary embodiments a short clear routine can be used to ensure thatthe droplet D is sufficiently separated from the electrode 2110. Suchshort clearing routines are known and need not be described in detailherein. In some exemplary embodiments, the duration that the electrode2110 is in a shorted state (during time 3119) can be measured. If theduration of the short exceeds a predetermined duration then it isdetermined that surface tension is not sufficient to pull the dropletoff and thus a short clear routine is initiated (for example, thecurrent can be controlled to pinch off the droplet), but if the short iscleared within the predetermined duration then no short clearingfunction is needed. In exemplary embodiments, the short durationthreshold is set in the range of 0.5 to 1 ms. The short durationthreshold can be set based on user input parameters such as WFS,electrode type, etc. In exemplary embodiments, if no short clear routineis needed (droplet transfer occurs easily) then the current can returnto the background level 3101 at point 3121. If needed, a short clear orpinch routine can be initiated at point 3121 to ensure proper droplettransfer. It is noted that the voltage and current waveforms in FIG. 30depict only a single droplet transfer.

Through the use of exemplary embodiments described above, travel speedssimilar to that have a purely DC+ waveform, but with much lower wirefeed speeds than traditional processes. This performance improvement isachieved along with reduced spatter and joint porosity as described.Embodiments of the present invention allow for any coating (e.g., zinc)to be burned off in a controlled manner and minimizes the absorption ofthe burned off zinc into the puddle. For example, embodiments of thepresent invention can achieve travels speeds in the range of 40 to 60in/min, while using wire feed speed in the range of 380 to 630 in/min.Further, as stated previously, exemplary embodiments can be used withboth solid and cored wires (metal or flux).

As explained previously, embodiments of the present invention allow fora weld to be created on coated materials (for example, galvanized steel)which has low porosity and spatter, but can be accomplished at highspeed with acceptable heat input. That is, exemplary systems similar tothat shown in FIG. 20 can be used with any of the exemplary waveformsdiscussed above to achieve greatly improved performance over knownsystems. For example, embodiments of the present invention can achievethe previously discussed porosity and spatter while welding at speeds inthe range of 10 to 150 in/min. In further exemplary embodiments, thewelding speeds are in the range of 30 to 80 ipm.

Further, in some exemplary embodiments of the present invention, thesystem of FIG. 20 can be used, but without the hot wire consumable 140and hot wire power supply 170. That is, exemplary embodiments of thewaveform shown in FIG. 29 or 30 can be used with generally traditionalwelding systems and provide improved welding performance of coatedmaterials over traditional systems. This is because embodiments of thepresent invention, allow for the escape of any vaporized coatings (e.g.,zinc) prior to puddle solidification.

In further exemplary embodiments of the present invention, at least oneof the wire 140 and electrode 2110 is enhanced to change the meltingtemperature characteristics of the weld puddle to further allow for theescape of any vaporized coating material. Specifically, either one, orboth, of the consumables 140/2110 is enhanced with an additional amountof at least one of Al, C and Si, or any combination thereof. Forexample, in some embodiments only the hot-wire 140 is the enhancedconsumable, while in other embodiments only the arc electrode 2110 isenhanced, and in even other embodiments both can be enhanced. Byenhancing the chemical composition of at least one of the consumableswith Al, C, and/or Si the melting point of the weld puddle is reducedand the melting range of the puddle is increased. Thus, the use ofexemplary embodiments of the enhanced consumables will extend the timethat its takes for the weld puddle to solidify on the workpiece 115. Byextending the solidification time, embodiments of the present inventionprovide further time for any vaporized coatings to escape from the weldpuddle. In fact, exemplary embodiments of the enhanced consumablesdiscussed herein can be used with any exemplary systems discussedherein. For example, the enhanced consumables can be used with anyexemplary system similar to that discussed in FIGS. 1, 14, 17, and 20,and any other systems contemplated herein, or where it is desired todelay the solidification of a weld puddle. For example, exemplaryembodiments of the present invention can reduce the melting temperatureof the weld puddle such that the weld puddle reaches 95% solidificationat a temperature in the range of 1400 to 1480° C., where the weld puddleis made in a workpiece that is coated mild steel. In embodiments, thecoating can be zinc. This is appreciably lower than traditionalconsumables which allow a puddle to reach 95% solidification at atemperature in a range of 1520 to 1550° C. Thus, embodiments of thepresent invention allow more time for any vaporized coating materials toescape—reducing porosity.

The enhanced consumables 140/2110 can be constructed, physically,similar to known consumables. That is, they can have a solid or cored(either flux or metal) construction. In some exemplary embodiments, theadded Al, C and/or Si is added to the composition of the consumablesintegrally. That is, the added Al, C and/or Si can be integral to thesolid wire composition, a metallic sheath composition or any flux ormetal core. In other exemplary embodiments, the additional Al, C and/orSi can be added to the consumables as an external layer on theconsumable. That is, an external coating or layer can be applied to theconsumable 140/2110 which contains any one, or a combination of, Al, Cand Si which will deposit this added material in the puddle to achievethe desired melting properties for the puddle. For example, a coating ofgraphite can be applied to a consumable via a vapor deposition process(or similar) to provide an added amount of carbon (C). This carbon willaffect the puddle reduce the puddle melting temp and widen the meltingrange as described above. Further, both Al and Si can be added via avapor deposition process (or similar) to provide a coating on theconsumables. It is noted, however, that if a coated consumable is usedit is desirable to use the consumable as a hot-wire consumable (e.g.140—FIG. 20) to ensure that the added material is sufficiently depositedinto the puddle. If the enhanced consumable is coated, and used as thearc electrode (2110), the arc could vaporize the coating before itenters the puddle.

As stated above, exemplary enhanced consumables have at least one or, ora combination of, Si, Al and C to improve the melting characteristics ofthe puddle. Specifically, exemplary embodiments can have an aluminum(Al) content in the range of 0 to 5% by weight of the consumable, acarbon (C) content in the range of 0 to 0.5% by weight of theconsumable, and/or a silicon (Si) content in the range of 0 to 2% byweight of the consumable. In further exemplary embodiments, theconsumable can have an aluminum (Al) content in the range of 1 to 5% byweight of the consumable, a carbon (C) content in the range of 0.001 to0.5% by weight of the consumable, and/or a silicon (Si) content in therange of 0.1 to 2% by weight of the consumable. It should be noted thatmany exemplary embodiments can have at least two of the above statedelements, which are combined in desired amounts, to achieve the desiredmelting profile of the puddle. Of course, these consumables would haveother elements to provide the desired weld composition and properties.Such elements and compositions are generally known and need not bediscussed in detail. That is, the enhancement of consumables discussedherein can be applied to many different types of consumables which areused to join coated steels, such as galvanized steel products. Forexample, one example of such a consumable can have C in the range of0.05 to 0.4% by weight of the consumable, Si in the range of 0.6 to 2.1%by weight of the consumable, and cerium (Ce) in the range of 0.35 to1.5% by weight of the consumable, where the combination of C, Si and Ceis in the range of 1.0 to 4% by weight of the consumable. Cerium is adeoxidizer that indirectly allows the silicon and carbon to stay insolution with the iron, and thus decreases the melting point of thepuddle. Other examples and combinations are contemplated herein, and theabove example is intended to be exemplary. For example, exemplaryconsumables constructed similar to that discussed in pending U.S.application Ser. No. 13/798,398, entitled CONSUMABLE FOR SPECIALTYCOATED METALS, can be used with embodiments of the present invention toachieve a desired puddle melt profile. This application is incorporatedherein by reference in its entirety, and in particular for consumablesthat can be used to join coated materials.

As explained previously, the exemplary enhanced consumables discussedherein provide a weld puddle composition which delivers an improved weldpuddle melt profile to allow for improved welding performance of coatedmaterials. The following discussion is directed to characteristics ofundiluted weld metal composition created by exemplary enhancedconsumables contemplated herein.

In first exemplary embodiments of enhanced consumables which use acombination of C and Si (in the consumable) to reduce the melt temp. ofthe puddle, the consumables provide an undiluted weld metal (which canalso be called an undiluted weld deposit) that has C in the range of0.05 to 0.3% by weight of the undiluted weld metal, and Si in the rangeof 0.6 to 2.0% by weight of the undiluted weld metal, where no Al isintentionally added to the consumable or the deposit (thus, to theextent Al is present it would only be in trace amounts). Thus, theconsumable composition (that is, the amount of C and Si) is selected toprovide the above stated ranges for each of C and Si. Of course, theundiluted weld metal will have other elements and compounds, which aregenerally known and need not be discussed herein. With these ranges, theundiluted weld metal will have improved melting characteristics withoutsacrificing weld strength or desirable weld properties. In furtherexemplary embodiments, the C is in the range of 0.1 to 0.3% and the Siis in the range of 1.0 to 2.0%, by weight of the undiluted weld metal.Such exemplary embodiments, may also include cerium (Ce). As statedpreviously, Ce is a deoxidizer which indirectly allows the silicon andcarbon to stay in solution, and thus aid in lower the melting temp ofthe weld puddle. In such embodiments, Ce is in the range of 0.35 to 1.5%by weight of the undiluted weld metal.

In further exemplary embodiments, which use a combination of Al and Si(in the consumable) to reduce the melt temp. of the puddle, theconsumables provide an undiluted weld metal that has Al in the range of2 to 5% by weight of the undiluted weld metal, and Si in the range of1.0 to 2.0% by weight of the undiluted weld metal. In these embodiments,the consumables can be such that little or no C is added to theundiluted weld metal from the consumable. That is, in such embodimentsthe C in the undiluted weld metal can be in the range of 0 to 0.06%, byweight of the undiluted weld metal, while in other embodiments C is inthe range of 0 to 0.03% by weight. Again, in embodiments where C is notadded by the consumable, it can be present in trace amounts. Again, theconsumable composition (that is, the amount of Al and Si) is selected toprovide the above stated ranges for each of Al and Si. Of course, theundiluted weld metal will have other elements and compounds, which aregenerally known and need not be discussed herein. With these ranges, theundiluted weld metal will have improved melting characteristics withoutsacrificing weld strength or desirable weld properties. In furtherexemplary embodiments, the Al is in the range of 3 to 5% and the Si isin the range of 1.5 to 2.0%, by weight of the undiluted weld metal.

In additional exemplary embodiments, which use a combination of Al and C(in the consumable) to reduce the melt temp. of the puddle, theconsumables provide an undiluted weld metal that has Al in the range of1 to 5% by weight of the undiluted weld metal, and C in the range of 0.1to 0.3% by weight of the undiluted weld metal. In these embodiments, theconsumables can be such that little or no Si is added to the undilutedweld metal from the consumable. That is, in such embodiments the Si inthe undiluted weld metal can be in the range of 0.01 to 0.25%, by weightof the undiluted weld metal. Thus, some Si can be present/added in theconsumable. Again, in embodiments where Si is not added by theconsumable, it can be present in trace amounts. Again, the consumablecomposition (that is, the amount of Al and C) is selected to provide theabove stated ranges for each of Al and C. Of course, the undiluted weldmetal will have other elements and compounds, which are generally knownand need not be discussed herein. With these ranges, the undiluted weldmetal will have improved melting characteristics without sacrificingweld strength or desirable weld properties. In further exemplaryembodiments, the Al is in the range of 1.5 to 4% and the C is in therange of 0.2 to 0.3%, by weight of the undiluted weld metal.

As stated above, the embodiments of systems and/or consumables discussedherein can provide improved spatter and porosity performance on coatedworkpieces, for example galvanized workpieces. This improved performancecan be attained on workpieces having galvanized coatings which are atleast 20 microns thick, on the welding surface of the workpieces. Ofcourse, embodiments of the present invention can be used on workpieceswhich much thicker coatings than 20 microns. That is, embodiments of thepresent invention can provide an undiluted weld deposit with an improvedporosity metric over known welding systems, methods and consumables,when welding coated materials. For example, exemplary consumables(discussed above), either alone or coupled with systems and methodsdescribed herein, can achieve the porosity and spatter performancediscussed previously in the present application. Additionally, aporosity metric in the range of 0.5 to 3 can be achieved when exemplarysystems have a travel speed at a rate of 50 in/min and a consumabledeposition rate in the range of 4 to 6.5 lb/hr. The same exemplaryconsumables can provide a porosity metric in the range of 0 to 1 when ata travel speed of 40 in/min and a deposition rate of 4 to 6.5 lb/hr. Asused herein, the porosity metric is the number of pores present in theundiluted weld metal which have an effective diameter larger than 0.5 mmover a unit length (inches). That is, a porosity metric of 2 means thatthere is an average of 2 pores—having an effective diameter larger than0.5 mm—per inch, along the undiluted weld metal. This is a porositymetric that cannot be attained by traditional systems, methods and/orconsumables. Further exemplary consumables discussed herein can providea porosity metric of 0.5 to 3 when at a travel speed of 50 in/min with aheat input in the range of 4 to 8 kJ/in, and provide a porosity metricof 0 to 1 when at a travel speed of 40 in/min with a heat input in therange of 4 to 8 kJ/in. Thus, embodiments of the present invention canprovide appreciably improved porosity performance on coated workpieces,without sacrificing weld integrity or properties, at low heat inputlevels and high speed welding. Thus, embodiments of the presentinvention provide welding systems, methods and consumables which allowfor welding coated materials at high travel speeds over a wide range ofheat input, with little or no porosity or spatter. In known systems, toachieve low porosity, the process had to proceed slowly with high heatinput (to slow the puddle cooling), which resulted in excessive heatinput. This excessive heat input can damage workpieces (especially thinworkpieces) and can vaporize excessive amounts of coatings (near theweld), which promotes corrosion. These issues are avoided withembodiments of the present invention.

The consumables discussed herein can be used with traditional weldingapplications (e.g., GMAW) and provide greatly improved performance, aswell as with exemplary systems and methods discussed herein to provideadditional performance improvements over traditional methods to weldcoated materials.

While the invention has been described with reference to certainembodiments, it will be understood by those skilled in the art thatvarious changes may be made and equivalents may be substituted withoutdeparting from the scope of the invention. In addition, manymodifications may be made to adapt a particular situation or material tothe teachings of the invention without departing from its scope.Therefore, it is intended that the invention not be limited to theparticular embodiments disclosed, but that the invention will includeall embodiments falling within the scope discussed herein.

1. A welding system, comprising: a welding power supply which createsand delivers a welding current to a consumable for deposition onto aworkpiece; wherein said welding current comprises a plurality of cycles,and where each of said cycles comprise: a background portion having anegative polarity and a background current level; a ramp phase portionfollowing said background portion which increases the polarity of saidwelding current from said background portion to a higher negativecurrent level using a first ramp rate; a negative peak portion followingsaid ramp phase portion having a negative peak current level which islarger than said higher negative current level and wherein a ramp rateof said welding current from said higher negative current level to saidnegative peak current level is larger than said first ramp rate; apositive pulse following said negative peak portion, said positive pulsehaving a ramp up portion, a peak portion and a ramp down portion, wheresaid ramp up portion has a first controlled ramp rate from a firstpositive current level to a positive peak current level of said peakportion, and said ramp down portion has a second controlled ramp ratefrom said peak level to a second positive current level; and a negativetail out portion following said positive pulse portion having a tail outcurrent peak level and during which a single droplet is transferred fromsaid consumable to said workpiece.
 2. The welding system of claim 1,wherein said first ramp rate is in a range of 25 to 100 amps/ms.
 3. Thewelding system of claim 1, wherein negative peak current level is in therange of 150 to 400 amps.
 4. The welding system of claim 1, wherein saidfirst positive current level is in the range of 50 to 200 amps.
 5. Thewelding system of claim 1, wherein said first controlled ramp rate is inthe range of 300 to 600 amps/ms.
 6. The welding system of claim 1,wherein said positive pulse peak level is in the range of 300 to 600amps.
 7. The welding system of claim 1, wherein said second controlledramp rate is in the range of 300 to 1000 amps/ms.
 8. The welding systemof claim 1, wherein said negative tail out level further comprises ashort circuit current portion during which said droplet is in contactwith said workpiece.
 9. The welding system of claim 1, wherein said tailout peak current level is below said negative peak current level andlarger than said background current level.
 10. The welding system ofclaim 1, wherein said second positive current level is a current levelwhere said power supply switches said welding current from positivepolarity to negative polarity.
 11. The welding system of claim 1,wherein at least one of said first ramp rate, a duration of said rampphase portion, said negative peak current level, a duration of saidnegative peak current level, said first positive current level, saidfirst controlled ramp rate, said positive peak current level, a durationof said positive peak current level, said second controlled ramp rate,said second positive current level and said tail out peak current levelare determined by said power supply based upon at least one of a wirefeed speed for said consumable and a type of said consumable.
 12. Thewelding system of claim 1, wherein at least one of a duration of saidramp phase portion; a duration of said negative peak current level, aduration of said ramp up portion, a duration of said positive peakcurrent level, and a duration of said ramp down portion are determinedby said power supply based upon a monitored voltage of said weldingcurrent.
 13. The welding system of claim 1, wherein said positive peakcurrent level is maintained until a predetermined threshold is reached,where said predetermined threshold is determined by said power supply tobe a threshold at which a tether between said droplet and saidconsumable has a diameter which is no more than 75% of the diameter ofsaid consumable.
 14. The welding system of claim 13, wherein saidpredetermined threshold is a dv/dt threshold.
 15. A method of welding,comprising: creating and delivering a welding current to a consumablefor deposition onto a workpiece; advancing said consumable towards saidworkpiece; wherein said welding current comprises a plurality of cycles,and where each of said cycles comprise: a background portion having anegative polarity and a background current level; a ramp phase portionfollowing said background portion which increases the polarity of saidwelding current from said background portion to a higher negativecurrent level using a first ramp rate; a negative peak portion followingsaid ramp phase portion having a negative peak current level which islarger than said higher negative current level and wherein a ramp rateof said welding current from said higher negative current level to saidnegative peak current level is larger than said first ramp rate; apositive pulse following said negative peak portion, said positive pulsehaving a ramp up portion, a peak portion and a ramp down portion, wheresaid ramp up portion has a first controlled ramp rate from a firstpositive current level to a positive peak current level of said peakportion, and said ramp down portion has a second controlled ramp ratefrom said peak level to a second positive current level; and a negativetail out portion following said positive pulse portion having a tail outcurrent peak level and during which a single droplet is transferred fromsaid consumable to said workpiece.
 16. The welding method of claim 15,wherein said first ramp rate is in a range of 25 to 100 amps/ms.
 17. Thewelding method of claim 15, wherein negative peak current level is inthe range of 150 to 400 amps.
 18. The welding method of claim 15,wherein said first positive current level is in the range of 50 to 200amps.
 19. The welding method of claim 15, wherein said first controlledramp rate is in the range of 300 to 600 amps/ms.
 20. The welding methodof claim 15, wherein said positive pulse peak level is in the range of300 to 600 amps.
 21. The welding method of claim 15, wherein said secondcontrolled ramp rate is in the range of 300 to 1000 amps/ms.
 22. Thewelding method of claim 15, wherein said negative tail out level furthercomprises a short circuit current portion during which said droplet isin contact with said workpiece.
 23. The welding method of claim 15,wherein said tail out peak current level is below said negative peakcurrent level and larger than said background current level.
 24. Thewelding method of claim 15, wherein said second positive current levelis a current level where said power supply switches said welding currentfrom positive polarity to negative polarity.
 25. The welding method ofclaim 15, further comprising determining at least one of said first ramprate, a duration of said ramp phase portion, said negative peak currentlevel, a duration of said negative peak current level, said firstpositive current level, said first controlled ramp rate, said positivepeak current level, a duration of said positive peak current level, saidsecond controlled ramp rate, said second positive current level and saidtail out peak current level based upon at least one of a wire feed speedfor said consumable and a type of said consumable.
 26. The weldingmethod of claim 15, further comprising determining at least one of aduration of said ramp phase portion; a duration of said negative peakcurrent level, a duration of said ramp up portion, a duration of saidpositive peak current level, and a duration of said ramp down portionbased upon a monitored voltage of said welding current.
 27. The weldingmethod of claim 15, wherein said positive peak current level ismaintained until a predetermined threshold is reached, where saidpredetermined threshold is determined by said power supply to be athreshold at which a tether between said droplet and said consumable hasa diameter which is no more than 75% of the diameter of said consumable.28. The welding method of claim 27, wherein said predetermined thresholdis a dv/dt threshold.